I wanted to illustrate the position dots in the upper margin of the sheets to show that the same identical plate was used. I overlaid my early plate proof on top of my late plate proof and scanned the top of the sheet.
I then did the same thing on the right edge of the sheets to show the right side guide dots as well. I then noticed the stamp images don't line up across the top or down the side.
I then measured the stamp designs. The proofs in the earlier sheet measure about 18.25 mm. X 22.75 mm. The proofs on the late sheet measure about 18.5 mm. X 22.5 mm. Apparently the sheets were printed on different papers that shrank differently after printing. Not only are the proof images different sizes but the margins between the stamps are also slightly different. When one looks at the stamps as singles they are perceived to be the same size but in reality they are not.
Wish I had the printing plate to measure as that maybe the only way to determine the intended size. The late plate proof is also mounted on card stock and the early proof is not.
If the printed sizes varied this much on the stamps it would have been very difficult to set up the perforation equipment which had to be done by hand with spacers set between the perforating wheels. If you had two or more different papers in the stock to be perforated it would be very labor intensive to re-space them every time a different paper was fed through the perforator. No wonder so many of these stamps are poorly perforated. I know these two proofs were done many years apart but it still illustrates that different sized stamps could be printed from the same plate.