Ottawa Tagging on The 1967-1973 Centennial Issue
The points of interest, where varieties occur, that will be discussed in today's post are:
- Variation in the chemical composition of the taggant compound: OP-2 versus OP-4 tagging.
- Variation in the colour of the tagging under UV light.
- Intensity of tagging bars in normal light.
- The width of the tagging bars.
- Tagging errors.
- Spacing of the tagging bars and configuration on the sheets.
- 3 mm OP-2 and OP-4 - BABN stamps and 6c black CBN sheet stamp: 21 mm
- 4 mm OP-4 booklet stamps and 6c black CBN sheet stamp with 4 mm OP-2: 20 mm
- 3.25 mm OP-2 CBN sheet stamps: 22.5 mm
- 4 mm OP-2 high value CBN stamps: 28 mm
- The spacing between the tagging bars is the same, no matter which position on the sheets we are looking at, and no matter which pane is being examined.
- The tagging bars generally extend the full length of the selvage in a block, except for blocks located in the bottom panes. On those blocks, the tagging stops just short of the bottom of the selvage. However, there is no evidence of any "next series of bands" that we often see on the Winnipeg tagged blocks from the centre panes. Generally, any block coming from one of the centre panes will show tagging that extends the entire length of the selvage.