The 1c Brown Northern Lights and Dogsled Stamp of the 1967-1973 Centennial Issue - Part Four

Today's post is the last to deal with the 1c value from this series, and will look at the booklet stamps that were printed by the BABN between 1971 and 1973, and perforated 12.5 x 12.

There were 6 booklets issued during this period that are listed in both Unitrade and McCann, which contained 1c stamps:

1. BK66, which was a 25c booklet that contained three 7c stamps. The single 1c stamp included in this booklet was located at the top right of the booklet pane. Consequently, it always has a straight edge on the right side. All of these booklet panes had PVA gum only. This booklet was issued on June 30, 1971.
2. BK67, which was a $1 booklet that contained twelve 7c stamps, four 3c stamps and four 1c stamps to make up the $1. It was also issued on June 30, 1971, but curiously it was issued with dextrose gum only. So all stamps from this booklet have dextrose gum and they are the only booklet stamps with this perforation to have dextrose gum. The four 1c stamps were located at the top of the booklet, so they can have a straight edge at either the right or the left, depending on which side of the pane they come from. 
3. BK68, which was the experimental 50c Toronto booklet, which was basically the same as BK66, but with an extra pane in each booklet. So all the stamps from this booklet still have PVA gum and a straight edge at the right. This was issued in August 1971.
4. BK69, which was the 25c booklet containing the 8c. This was a very complicated booklet that contained three 1c stamps: two on the top row and one in the middle row on the right. These booklets only had PVA gum, but the stamps can have a straight edge at either the right or left. The first of these were issued on December 30, 1971. 
5. BK70, which was the $1 booklet containing the 8c. There were six 1c stamps in this booklet, occupying the top three rows. This booklet had a very shiny, PVA gum that was quite different from the other booklets. So mint singles can be identified as having come from this booklet based on the appearance of the gum. Singles can have a straight edge at right or left, depending on which side of the booklet they come from. This booklet was issued on December 30, 1971. 
6. BK71, which was a new 50c booklet, adopted after the Toronto experiment involving BK68 had proved successful. This one had four 1c stamps in it: one on the top right, two on the second row and one on the third row at left. Again, they could have straight edge on either side, depending on which side of the booklet they come from. This booklet was issued in August 1972. 

One obvious question that arises is whether or not it is possible to distinguish the stamps that came from each of these booklets based on their paper fluorescence, tagging and other physical characteristics. 

Unitrade gives ten listings for untagged singles (#454e to #454eix), and nine for the tagged stamps (#454ep to #454epvii). I would contend that there are quite a few more than 19 varieties of these stamps, and I believe that with careful attention to detail, most singles can be identified as to which booklet they came from. 

So for the remainder of this post, I will look at the booklet singles from each of the above 6 booklets and will then conclude with some sorting tips to identify which booklet the singles in your collection come from. 

BK66 - Stamps From the June 30, 1971 25c Booklet

Shades

The shade of brown used to print these stamps is similar to that found on BK67 below, which is to say a deep chocolate brown. However, there is just the slightest hint of purple to the shade. The inks appear almost black under UV, so I would say that the ink used to print these stamps is transformative in nature. 

Paper

The paper used to print these stamps is very hard and stiff, at least when the gum is on. The paper bends easiest in the vertical direction, which indicates that it is a vertical wove. There is a light vertical ribbing on the surface, which is easiest to see when the stamps are viewed against strong back-lighting. Under magnification, the paper appears uncoated and although smooth, there are, what appear to be minute loose fibres on the surface. The paper is strongly cream coloured, when viewed against a white background. 

Gum

The gum used on these booklets is a smooth PVA that had a satin sheen, and an obvious cream colour. This is easiest to see, by showing it next to one of the later printings made with white PVA gum, from BK69:

The pair shown on the left is the same pair shown in the first scan, while the one on the right is a pair from BK69, which has a much whiter PVA gum. 

Paper Fluorescence

Unitrade lists only two grades of fluorescence on these stamps: low fluorescent (LF) and medium fluorescent (MF), while McCann lists these, in addition for dull fluorescent. All three of these descriptions are a little inadequate, I find, because they ignore the fluorescent fibres that are visible in the paper as well as the brownish woodpulp flecks. 

The basic colour of the paper under UV is a light violet grey on the front and a bluish white on the back. All through the paper are brownish woodpulp flecks, that become visible when you look at the paper very closely under UV. There are fluorescent fibres embedded in the paper that vary both in brightness, and density. It is these variations that give the paper its overall appearance:

• A sparse to very sparse density of dull fluorescent fibres results in paper that McCann calls "dull". It is much scarcer than either the low fluorescent or medium fluorescent papers. 
• A low density concentration of dull fluorescent fibres and a very sparse concentration of medium fluorescent fibres results in the low fluorescent paper, which is the most common paper found on these booklets. 
• A higher density of medium fluorescent fibres results in the so called medium fluorescent paper. 

The paper of the stamps containted in the other booklets do not show the brownish woodpulp flecks so clearly. A loupe is required to see them clearly, but they are much, much more prominent on the stamps from this booklet than any other. 

Tagging

All of the stamps from these booklets are untagged. 

BK67 - Stamps From the June 30, 1971 $1 Booklet

Shades

The brown of these stamps contains more red than most of the other booklet stamps, but is not red-brown. On the Gibbons colour key, the colour is a deep chocolate brown. The ink appears the same colour under UV light that it does in normal light, which indicates that the inks used are non-transformative. 

Paper

The paper of the stamps from this booklet has a soft feel to it. It bends easily in the horizontal direction, so it is horizontal wove. Under magnification it has a smooth, uncoated surface and is never ribbed on either the front or the back. When viewed against a white background, the colour of the paper is a creamy off-white. No mesh is visible, when the paper is viewed against strong back-lighting. 

Gum

The gum on these stamps is a smooth, creamy dextrose gum that has a semi-gloss sheen. There are often very fine horizontal striations in the gum that resemble fine brush strokes. When viewed against a white background and compared to other PVA gum stamps, it appears a deep cream colour, as shown in the scan below:

The stamp with dextrose gum is shown on the left, next to a PVA gum stamp on hibrite paper, that came from BK69. The difference in colour is quite striking. 

Paper Fluorescence

The paper of these stamps appears a light bluish grey under UV light, with a very sparse concentration of medium or high fluorescent fibres visible in the paper. 

Tagging

None of the stamps from these booklets are tagged. 

BK68 - Stamps From the August 50c Experimental Toronto Booklet

These booklets were simply made by taking BK66 and gluing an additional pane into the front cover to make a 50c booklet. Consequently, the physical properties of the stamps are exactly the same as they are for all the BK66 stamps that I observed. 

BK69a-y - Stamps From the December 30, 1971 25c Booklets With The Plain Covers

Shades

On these booklets, the printing appears somewhat weak. The shade of the ink is quite reddish, whereas the printings on the later versions of this booklet are printed in deep brown shades that lack the reddish undertone of these ones. The stamp on the left is slightly redder than the one on the right. The shade is a deep purple brown on the Gibbons colour key. This colour appears essentially the same under UV light, which indicates that the inks used are non-transformative. 

Paper

The paper used for these stamps has a slightly whiter appearance on the front, when viewed against a black background. McCann lists two sub-types of this paper:

1. A vertical ribbed paper in which the ribbing is only faintly visible on the paper surface, but becomes very pronounced, when the stamps are viewed against strong back-lighting. This is a vertical wove paper, and it has a very smooth, uncoated surface. Occasionally, little minute depressions are visible in the paper's surface. 
2. A vertical wove paper that does not show any ribbing at all, even when viewed against strong backlighting. This paper appears almost as smooth under magnification, as the first paper above, but loose fibres are visible on the paper surface, under magnification. 

Gum

The gum used on these printings was a whiter PVA, with a satin sheen. The white gums that are shown in the various comparison scans above are examples of this gum. 

Paper Fluorescence

According to Unitrade, the paper used on these booklets exists in five grades of fluorescence, while according to McCann, the number of grades of fluorescence that are reported to exist, depends on whether or not the paper is the ribbed paper or not:

1. Ribbed paper is reported to exist in low, medium and high fluorescent grades.
2. Smooth (non-ribbed) paper is reported to exist in low, medium, high fluorescent and hibrite grades. 

According to McCann, none of these booklets exist with dull fluorescent paper. Thus it is logical to conclude that Unitrade's dull fluorescent listings for these booklet stamps, must have come from the later printings with the 10 cover designs in brown. 

The picture below shows the low fluorescent, high fluorescent and hibrite papers, as listed by McCann:

The lighting conditions in which this picture was taken make everything look a little duller than it is. For instance, the low fluorescent paper in this picture appears dull, but is actually low fluorescent. 

1. The low fluorescent paper appears a greyish white colour on the front, and a bluish white colour on the back under UV light. There are a few brownish woodpulp fibres visible here and there on the paper, but not many. There is what can best be described as a low density concentration of low fluorescent fibres, and a sparse concentration of medium fluorescent fibres visible in the paper. 
2. The medium fluorescent paper is a greyish colour under UV, but has a medium density concentration of medium fluorescent fibres that give it a medium fluorescent appearance. 
3. The high fluorescent paper is a greyish white colour under UV, but has a medium density concentration of low and medium fluorescent fibres, which makes it appear as high fluorescent. There are no brownish woodpulp fibres visible in this paper. 
4. The hibrite paper is a medium fluorescent bluish white colour under UV, but there is a high density concentration of medium and high fluorescent fibres that make the paper appear hibrite overall. 

Tagging

According to McCann, there were some printings that were made with 4 mm Op-4 tagging that gave a light green glow under UV, as shown in the picture above. He lists the tagged stamps as existing on three types of paper:

• Smooth, medium fluorescent.
• Smooth, high fluorescent. 
• Ribbed, high fluorescent. 

BK69aa-69as - Stamps From the August 1972 25c Booklets With the Themed Covers

These booklets are the most complicated of the bunch, due to the use of two different papers, multiple levels of fluorescence, different shades, and two different kinds of tagging. 

The shades on the 1c stamps from these booklets seem to depend on the paper and tagging type. 

This shade is deep violet brown and was found on a smooth paper stamp, with OP-4 tagging.

This shade is a little brighter, being more of a purple brown. It was also found on a smooth paper stamp with OP-4 tagging. 

These two shades were found on smooth paper booklets also. The left stamp is a deep violet brown, and occurred on a booklet that had no tagging and high fluorescent paper. The right stamp was found in a booklet on medium fluorescent paper, with 3 mm OP-2 tagging, and is a deep chocolate brown on the Gibbons colour key.

These two stamps both come from booklets printed on vertically ribbed paper. The stamp on the left is from an untagged booklet on dull paper, while the right one is from an OP-2 tagged booklet on high fluorescent paper. The left stamp is a deep chocolate brown on the Gibbons colour key, while the right stamp s deep brown.

So, from my study of the stamps and booklet panes, there would appear to be four shades possible:

• Purple brown.
• Deep violet brown
• Deep chocolate brown
• Deep brown

It is not clear whether all four shades can be found on every paper and tag type. It seems from my small study that this is NOT the case. It seems rather, that 1 or 2 of the shades can be found on a particular paper and tag type. But, my study did not involve a particularly large sample of booklets, and a larger study may reveal that all four can be found with most varieties. 

Under UV light, the colours generally retain their nature, except on the high fluorescent papers, where they look almost black. So the inks would seem to be largely non-transformative. The black appearance of the ink on the higher fluorescent papers may be a visual trick that the fluorescence is playing on our eyes. However, it is possible that different, transformative inks were used. 

Finally, some stamps show very distinct blackish, or greenish discolouration on the sides of the design. This is contamination from the black and slate inks used on the other stamps in the booklet. We don't generally see this with the stamps from the other booklets. So this discolouration can be an aid to identifying singles from BK69.  

Paper

There were two basic types of paper used to produce these booklets:

1. A horizontal wove paper that shows no ribbing on the surface and in fact is smooth, and under magnification appears to have a very light surface coating. 
2. A horizontal wove paper that shows clear vertical ribbing on the face, that is not visible in back-lighting, but can be easily seen under magnification, and to a lesser extent, by viewing stamps at an angle to the light. The ribbed paper appears to also have a very light surface coating.

McCann makes no specific mention of this difference on these booklets, but only those with the plain covers, issued earlier. Neither does Unitrade. Unitrade only acknowledges ribbed paper on BK71, but it very clearly exists on these booklets. What is not clear from the study I have done, is what the full range of tagging and fluorescence varieties is on this paper type. I have found dull paper, with no tagging and high fluorescent paper with OP-2 tagging, which I will illustrate and describe. But so far, that is all I have found in looking through over 100 booklets. However, that is a very small sample, and there may well be, and probably are, more varieties. 

Gum

The gum used on these booklets is a very slightly off-white PVA gum with a satin sheen. It appears dead white compared to the gum on say, BK66, BK68 or BK70.

Tagging

There were three two types of tagging found on these booklets:

1. A pale green OP-4 tagging that was 4 mm wide, as shown above, and 
2. A bright greenish yellow OP-2 tagging that was 3 mm wide and shown below

Note how the tagging bars on this booklet do not extend all the way to the top of the tab on the pane. Below is an example of another printing in which the tag bar runs the full length of the pane.

Distinguishing the tagging can be difficult for some collectors because the OP-4 tagging on these booklets does not show the same fading and migration that OP-4 tagging on the 1972-78 Caricature issue shows. However, it does migrate onto the booklet covers, and if you examine the covers of complete booklets, you can usually see some evidence of migration from the panes. In any event, the OP-4 tagging is generally always a pale green under UV and is 4 mm wide, whereas the OP-2 has more of a bright yellow appearance, and is always 3 mm wide. 

Paper Fluorescence

According to Unitrade and McCann, the untagged stamps exist with all the major grades of fluorescence:

• Dull fluorescent
• Low fluorescent
• Medium fluorescent
• High fluorescent
• Hibrite

According to Unitrade and McCann, the OP-4 tagged stamps exist only with low, medium and high fluorescence, while the OP-2 stamps exist with five grades of fluorescence:

• Dead (non-fluorescent)
• Dull fluorescent
• Low fluorescent - Unitrade does not list this, but McCann does.
• Medium fluorescent
• High fluorescent

These discrepancies are useful in assisting collectors in the task of distinguishing the different levels of fluorescence. For example, neither of the tagged stamps are reported to exist with the hibrite paper, which suggests that if you come across panes that are tagged, that appear to be hibrite, chances are they are high fluorescent, rather than hibrite. Likewise the dead paper is only reported to exist on the OP-2 tagged panes, so that panes that untagged panes on apparently dead paper, are probably just dull. Starting your study with the OP-4 tagged panes is useful because they do not include the fluorescence levels at the extreme ends of the scale, i.e. no dull, no dead and no hibrite. So if you have enough of them to sort, you can get a good feel for the differences between low, medium and high fluorescent papers. 

Because neither McCann, nor Unitrade differentiate between smooth and ribbed papers, it is not clear whether some of these levels of fluorescence exist only with one type of paper and not the other, or whether they exist with both. 

The various pictures below show some of these varieties, which I will attempt to describe, as the same overall fluorescence level can show differences in terms of the overall colour under UV, as well as the concentration and brightness of fluorescent fibres contained within the paper, as well as brownish woodpulp flecks.

We will begin with the medium and high fluorescent papers on the OP-4 tagged booklets:

The high fluorescent paper is on the left. It is basically a medium fluorescent bluish white paper under UV that contains a low density concentration of high florescent fibres, which give the paper an overall high fluorescent appearance. On the back, the paper appears bright white, and under magnification you can see a medium to high density mass of fluorescent fibres that do not stand out, which suggests that on the back the paper is high fluorescent, and the fibres are high fluorescent. 

The medium fluorescent paper is shown on the right. It is a dull fluorescent greyish paper under UV that contains a low density concentration of low fluorescent fibres and a sparse concentration of medium fluorescent fibres, that give it an overall appearance of being medium fluorescent. If we look at the back of the pane, we see that the paper is also dull fluorescent greyish, with a medium density concentration of low fluorescent fibres and a low density concentration of medium fluorescent fibres. These give the paper a medium fluorescent bluish white appearance overall, as seen from the back. I don't think there is really any difference in fluorescence levels on the front and back, but the true fluorescence shows more clearly on the back, without the printed design to distract our eyes. 

Next, we have an untagged pane on smooth, high fluorescent paper and an OP-2 tagged pane on smooth medium fluorescent paper:

The booklet on the right is an example of the OP-2 tagging on medium fluorescent paper, while the untagged pane on the left is on high fluorescent paper:

• The high fluorescent paper is actually a dull fluorescent greyish paper that contains a medium density concentration of low, medium and high fluorescent fibres. Together, these give it the appearance of being HF. On the back, the paper is dull fluorescent greyish, with a low density concentration, of low, medium and high fluorescent fibres that give the paper an overall HF appearance. This paper is clearly different from that used on the OP-4 booklets in that the colour under UV is bluish white rather than white, and the fluorescent fibres show up much more clearly because the ambient level of fluorescence in the paper is only dull. 
• The medium fluorescent paper is a dull fluorescent greyish paper containing a low density concentration of low fluorescent fibres, a sparse concentration of medium fluorescent fibres, and a sparse concentration of brownish woodpulp fibres. Together, these give the paper an overall MF appearance. On the back, the paper is dull fluorescent greyish with a low density concentration of low fluorescent fibres and a sparse concentration of medium fluorescent fibres, that give it an overall MF appearance. Again, this paper is slightly different from that used to produce the OP-4 tagged booklets on MF paper, in that the concentrations of low fluorescent fibres and medium fluorescent fibres are lower, which gives it a bluish appearance under UV, rather than a bluish white appearance. 

Now lets take a look at two of the ribbed papers: one on dull paper, and the other on medium fluorescent paper with OP-2 tagging:

The dull paper is shown on the left. The type shown here is actually a non-fluorescent violet paper under UV that contains a low density concentration of low fluorescent fibres, which raises the fluorescence level overall from dead to dull. It appears exactly the same on the back and the front.

The medium fluorescent paper used on this printing is different again slightly from the other medium fluorescent papers shown so far. On the back, it is still bluish, but clearly brighter than the other OP-2 booklet with the short tagging bars, but not quite as bright as the OP-4 booklet, which suggests to me that the ambient level of fluorescence is a little higher, like say a dull fluorescent greyish white, rather than a grey. There appears to be a medium density concentration of low fluorescent fibres, and a low density concentration of medium fluorescent fibres, visible in the paper. So there is a higher concentration of fibres in this paper than the OP-2 paper. But overall, it is still medium fluorescent.

This leaves low fluorescent paper, and hibrite paper, which I haven't shown yet. Unfortunately I do not have a hibrite example to show here, but will add one when I come across it. Fortunately I do have two very slightly different low fluorescent papers: one smooth, with OP-2 tagging, and the other ribbed without tagging. The pictures below show both types:

Clearly the tagged pair looks a little brighter than the right stamp, but it is not bright enough to be medium fluorescent. The overall appearance of the tagged pair on the front is bluish, but under magnification you can see you can see that the paper is a dull fluorescent deep grey, with, what seems to be a sparse concentration of medium fluorescent fibres that are raising the overall perceived fluorescence level from dull to low. The stamp on the right appears dull fluorescent grey under UV, with a sparse concentration of both medium fluorescent fibres and brownish woodpulp specks, that overall, raise the perceived fluorescence from dull to low.

Let's take a look at the backs:

On the tagged pair, the paper appears bluish white overall. Under magnification, it is clear that the ambient fluorescence level is dull fluorescent greyish white. There is a low density concentration of low fluorescent fibres, and a sparse concentration of medium fluorescent fibres, as well as a very few brownish woodpulp fibres that give it a MF appearance on the back only. 

The stamp on the right is dull fluorescent deep greyish under UV, with a low density concentration of low fluorescent fibres, a sparse concentration of medium fluorescent fibres and a sparse concentration of brownish woodpulp flecks. Overall this gives a low fluorescent greyish appearance. 

So far, all of the booklets from this group that I have looked at do not show significant levels of brownish woodpulp fibre in the paper. The woodpulp fibres are something that we typically see in stamps issued between 1972 and about 1974. As we shall see, BK71 is printed on paper that usually shows the same level of woodpulp fibres as the stamp shown above does. So it is possible that it comes from BK71 rather than BK69. However, BK69 would have been issued until the 25c Caricature booklet replaced it in April 1974. So what seems much more likely to me is that the initial printings of these booklets were on smooth paper, and then the last printings, made between 1972 and 1974 were on the ribbed paper. This seems consistent with my observation that there are no OP-4 tagged booklets with ribbed paper, as OP-4 tagging had been replaced by OP-2 at this point. Most all of the fluorescence levels found in the period from 1971 to 1972 are also found up until 1974, so I would think that the ribbed papers and smooth papers would exist with the same levels of fluorescence. 

BK70 - Stamps From the December 30, 1971 $1 Booklet

Shades

The shade of ink used on these stamps lacks the reddish and purple undertones of the other booklets and is closest to Gibbons's deep brown. 

Paper

The paper used for these booklets is a horizontal wove that shows clear vertical ribbing when viewed against strong back-lighting. Under magnification, there appears to be a very light coating on the paper surface that gives it a satin sheen, and the ribbing is very faintly visible. The paper appears noticeably creamy when viewed against a white background:

You can clearly see that the paper is off-white, though it is not as creamy as the paper from BK66 and BK68 for instance. 

Gum

The gum used for these booklets is very distinct. It is a thick PVA that had a semi-gloss sheen, almost appearing to be a cross between dextrose gum and PVA. The thickness of this gum usually causes stamps with it to curl horizontally. 

Paper Fluorescence

The paper used to print these booklets is a dull fluorescent paper, that contains no visible fluorescent fibres, nor any brownish woodpulp flecks. Under UV it appears a greyish colour. 

Tagging

Some of the booklets issued had 4 mm OP-4 tagging that glowed light green as shown in the picture above. 

BK71 - Stamps From the August 1972 50c Booklets

Shades

I have found two distinct shades on the stamps from these booklets. The first is shown below:

The shade shown here is a deep violet brown. It is not shown in the Gibbons colour key, but it is close to both the deep brown and the purple brown, but it is more purple than the dark brown and deeper than the purple brown that are shown on the key. 

The second shade is shown below:

This one is brighter than the last, and a true match to Gibbons's purple brown. 

Paper

The paper used to print these booklets is a vertical wove paper that is very strongly ribbed, with the vertical ribbing being very obvious when the stamps are examined under magnification, viewed at an angle to the light, or viewed against strong back-lighting. The printed surface of the paper appears very smooth under 10x magnification, but uncoated and somewhat porous. 

Gum

The gum found on these stamps is a white PVA with a satin sheen. 

Paper Fluorescence

Both Unitrade and McCann list two grades of fluorescence: low and medium. However, there are actually at least four types of paper, which are close variations of the two basic varieties. Before I get into those, I will illustrate the two basic types of paper fluorescence in the picture below:

The medium fluorescent paper is shown on the left, and the low fluorescent paper on the right. Again, the lighting conditions make both papers appear less bright than they actually are. 

Both papers contain brownish woodpulp fibres, as well as fluorescent fibres. So the variations of paper that exist, in addition to the basic two shown above, are those in which the concentration and brightness of these additional elements varies as follows:

1. One paper is dull fluorescent greyish under UV, with a low density concentration of low fluorescent fibres, a sparse concentration of medium fluorescent fibres, a very sparse concentration of high fluorescent fibres and a sparse concentration of brownish woodpulp fibres. Together, these give the overall appearance of medium fluorescent paper. 
2. One paper is dull fluorescent greyish white under UV, with a low density concentration of low fluorescent fibres, a sparse concentration of medium fluorescent fibres, very few high fluorescent fibres and a sparse concentration of brownish woodpulp fibres. Together, these give the overall appearance of medium fluorescent paper. 
3. One paper is dull fluorescent deep grey under UV, with a low density concentration of low fluorescent fibres, a very sparse concentration of medium fluorescent fibres, and a sparse concentration of brownish woodpulp fibres. Together, these give the overall appearance of low fluorescent paper. 
4. One paper is dull fluorescent greyish under UV, with a sparse concentration of low fluorescent fibres, a very sparse concentration of medium fluorescent fibres, and a sparse concentration of brownish woodpulp fibres. Together, these give the overall appearance of low fluorescent paper. 

Tagging

Some of the booklets printed exist with OP-4 Ottawa tagging as shown above. However, instead of the bands being 4 mm wide as before, the bands are always 3 mm wide. The picture above shows both types of paper, with the medium fluorescent paper on the top, and the low fluorescent paper on the bottom. Note how much brighter and yellowish the tagging of the top pair appears, as compared to the pale green tagging of the bottom pair.

Conclusions: Sorting Single Booklet Stamps

As we have seen, despite the apparent similarities of the booklet stamps, there are characteristics of each booklet that allow us to assign individual stamps to a particular booklet. The only exception to this is possibly BK68, which used the exact same panes as BK66, so it is only possible to assign singles to either BK66 or BK68.

If you have pairs of stamps from a booklet, it may possible to assign those to a particular booklet right away, based on the layout of the stamps, which are specific to a particular type of booklet:

1. A stamp with a label at left, must come from either BK66 or BK68.
2. A vertical pair of 1c and 3c stamps can only come from BK67.
3. A vertical pair of the 1c and 7c can only come from BK 66 or BK68.
4. A vertical pair of the 1c and 6c, with the 6c on the bottom can come from either BK69, or BK70, but if it comes from BK70, the pair will be heavily folded from where the pane was folded originally. 
5. A vertical pair of the 1c and 6c, with the 6c on top can only come from BK71.
6. A vertical pair of the 1c and 8c, with the 8c having straight edges on 2 sides must come from BK69.
7. An unfolded left vertical pair of the 1c and 8c must come from BK71, as the pairs coming from BK70 would be folded through the middle.
8. A horizontal pair of the 1c and 6c must come from BK69.
9. A horizontal pair of the 1c and 8c must come from BK71. 

In terms of sorting singles, the gum is the best attribute to start with, if you are sorting mint stamps:

1. If the gum is a cream coloured PVA gum with a satin sheen, it is from either BK66 or BK68.
2. If the the gum is white PVA it comes from either BK69 or BK71.
3. If the gum is the thick shiny PVA with the cream colour that causes the stamps to curl horizontally, then it is from BK70. 
4. If the gum is dextrose gum, then it is from BK67. 

So, after doing this sort, the task that remains is to sort the BK69 from BK71 singles. The next best characteristic to do this in my opinion is to look for brownish woodpulp fibres under UV light and to look for ribbed paper. So I would sort any remaining stamps into two piles:

1. Those on smooth paper, with no ribbing: these must come from BK69. It may not be clear whether they come from the earlier 1971 booklets with the plain covers or the later booklets, but they do come from one of the 25c booklets. The next task will be to sort those further.
2. Those on ribbed paper: these will come either from BK69 or BK71.

Then I would take the ribbed papers and sort them further by looking for those papers that are either low fluorescent, or medium fluorescent and which contain at least a sparse concentration of brownish woodpulp fibres, as these are from BK71. That leaves the rest of those stamps as being from BK69. 

Then, with the remaining BK69 stamps on the smooth and ribbed papers, look now for tagged stamps with 3 mm OP-2 tagging. Those must come from the later 1972-74 BK69's. That leaves you with OP-4 tagged stamps, which can come from either the 1971 or 1972-74 booklets, and untagged stamps. 

The next thing to look for is tricky and requires experience, and that is the appearance of the paper under magnification. You are looking for paper that appears to have no surface coating, and where you can see small loose fibres on the paper surface, or minute depressions in the paper, as these will come from the earlier BK69's. All the later BK69 stamps lack the depressions in the paper and they all have a very light surface coating, which prevents any loose fibres from appearing on the paper surface. The ribbing of the earlier paper is also much more pronounced when viewed against back-lighting that the later booklets, where you can barely see it against back-lighting. Applying this test corectly will allow you differentiate singles from BK69a-y (McCann) or BK69a-c (Unitrade) from all the others (BK69aa-as in McCann and BK69d-k in Unitrade). You can then go about sorting the different levels of paper fluorescence. You can also use shades to a lesser extent: deep brown stamps,without any hint of purple or red, will likely be from the later BK69's, but most other shades will exist with either the earlier or later booklets, so they are not very useful for separating printings into the earlier or later BK69's. 

If your stamps are used, the sorting is more difficult, but is still doable. But you have to start with the paper first because you cannot use gum. First, sort the papers into cream paper and white paper (very light cream). Cream papers will be from either BK66, BK67, BK68 or BK70. White papers will come from either BK69 or BK71.

Taking the cream papers, sort them into horizontal and vertical wove paper depending on which direction the paper bends most easily, without creasing. Horizontal wove will come from either BK67 or BK70. If you sort these into ribbed and smooth papers, the smooth papers are BK67 and the ribbed ones are BK70. The vertical wove papers will all be either BK66 or BK68, and they should be ribbed vertically. 

Taking the white papers, sort them into vertical and horizontal wove papers. The vertical wove papers can come from either the early BK69's or the BK71. Look in this group for non-ribbed, smooth paper. Those stamps must come from the early BK69's. This leaves you with the ribbed papers, which can be early BK69, or BK71. To sort these, look under UV light for brownish woodpulp fibres. If the paper is either low fluorescent or medium fluorescent with obvious woodpulp fibres, it is from BK71.  You can then conclude that the remaining stamps on vertical wove paper are early BK69's and can then sort the different paper fluorescences and tagging, etc. 

This leaves you with the white papers that are horizontal wove. All of those should come from the late BK69's from 1972-74. There will be a mixture of ribbed and smooth papers, tagged and untagged, as well as different fluorescence levels, which you can then sort, accordingly. 

This takes us to the end of the 1c stamp. Next week I will look at the printings of the 2c green untagged stamps in next week's post, including the stamps from the 1970 OPAL booklet.