1cent1 Unusual Perforation Size 10 And 3/4 ? [much Better Images Added ...]

Two of my stamps, both on covers and both from the left side margin of the sheet, have this really confusing perforation size: 10 3/4![The gauge I use is a 'Lighthouse'. Also, I measured the perforations with a calibrated ruler: same 10 and 3/4 per any 2cm measured. None of the other sizes - like 10, 10.5 or 11 get to match the perforations as well as the 10 and 3/4 ...]
They seem flat plate and the size of the design is 19mmX21.85mm: these two stamps are the first 1cent1 I found with the height less than 22mm.
My logic is that paper shrinkage would occur along the fibers of the paper and would alter only one of the two: height or width. ... and there are two of them, each on different covers of different types of paper.
Below is one of the stamps showing 10 and 3/4 perforations, on all three perforated sides. The red stamp is perf 11.




To make sure, I compared the perforations with that of another 10and 3/4 stamp: Scott#3422 which has the vertical perf 10 and 3/4. Below you can see the result:



... and digital processing to compensate for my shaking hands:

A perforation gauge is not a measuring tool. It counts perforations between two lines 2 millimeters apart. the stamp appears to be a normal perf 11-72 using a Kiusalas or Multi-Gauge based on English measurement of 0.072 inch spacing between perforation holes on a line perforator. Rotary press perf 11 on the bar perforator was set up with pins spaced 0.070 inch apart.

Paper shrinkage across the paper grain occurred after printing and before gumming and perforating.

So, there was definitely no perforation 10 and 3/4 used in the era?

see the post above which included important information. you need a US perforation gauge to get the correct results. of course you can also use the standard perforation gauges, but then you will get such results between the normal 10, 10.5, 11 and so on.

The question still remains: was there a perforation of 10 and 3/4 used for US stamps before 1930, please?
The first such perf appears in US Scott to be used in 1975, but other countries were using it decades before ...

see above :)
you can either compare with other perf 11 stamps or use a US gauge and check the 11-72.

Stamperix, I did compare them with other perf 11 1cent1s
I even compared them at a very high resolution and did all the possible measurements. It looks that whatever I do the bloody stamps show perf 10 3/4 and the height remains 21.85mm which makes them a tad shorter than any 1cent1 in my albums ...
Online, I found a couple of older posts mentioning the same perf 10 3/4 being found by the authors, but without images of their stamps.
Most likely, I will have to dig deeper
... and to buy a US gauge

Line perforator pin spacing was determined by the number of pins that would fit equally spaced around a cylinder of a standard size. This limitation also applied to horizontal or vertical perforations on rotary press applied in the direction of the web. Perforations at right angles to the rotary press web (all coils and one direction on sheet stamps) were punched by a bar perforator. I haven't seen any references in the literature linking US perforating equipment of the period with foreign manufacturers.

To accurately assess stamp size, compare with other stamps from the same issue. Different denominations are OK as long as the baseline stamp can be unambiguously identified. Measuring stamps with a ruler is futile.

what I would like to know some time now: why is the 10.5 on the US Kiusalas the same than on regular (European) perforation gauges? Or isn't it exactly the same?

Maybe Kiusalas 11-73=10.79 but more like the new Kiusalas 11-72.5=10.86 which is well known to occur. It has even been included in the U.S. Multi Gauge at http://www.slingshotvenus.com/stamp...tyPerf5.html

http://stampsmarter.com/learning/Ma...rations.html
Don