Constant Plate Flaws on the 1967-1973 Centennial Issue
1c Northern Lights and Dogsled Team - Airplane in Sky
This variety is found on selected 25c booklets printed by the BABN that contained the 1c, 6c and 8c stamps, that were first issued on December 30, 1971. It is constant in the sense, that it is always found on the same stamp when it occurs: the 1c stamp from the middle row of the booklet. It is quite a prominent variety, being visible to the naked eye, without a magnifying glass. However, it is not found on every example of the 25c booklets that were printed, but only on a few printings. It consists of a blob of colour appearing in the sky roughly in the middle of the design as shown in the above scan.
The scan below shows the booklet that it comes from:
5c Atlantic Fishing Village - Line in 5
5c Atlantic Fishing Village - Broken Necklace
It consists of a shadow of a double "C" for the "C" in "Canada", that is placed just to the right of the main letter on the inside. Unitrade notes it's position on the sheet as position 10, but makes no note of whether it comes from plate 1 or plate 2. It is listed as having come only from the perf. 10 printings, which means that it must have originated from one of these two plates. Curiously enough, Unitrade does not list a plate block for this variety, which is odd, because every upper right corner block from the upper right pane should have this variety, if it is indeed from position 10.
The above example comes from Douglas Karns, and is indeed from an upper right field stock block, in position 10.
8c Parliamentary Library - Extra Spire