chgk, Pause for a bit and digest a couple of things. 1. Stop measuring with the millimeter rule No, really stop. It is unfortunate the catalogs give this data and collectors try to use it first. It should be used last, if at all. 2. The perforation rate in most catalogs is rounded to the nearest half. It is seldom exactly 10 or 11 or 12. While you have an alignment close to 11.25, it will be "perf 11" in the catalog listings. 3. The perforation rate at the sides can also be different and needs to be gauged too. In the case of your stamp, you will find it to be closest to 10.5 4. Having gauged your stamp and found it to be 11 at top/bottom and 10.5 at the sides, it can only be Scott 632 (which is also typical of this shade of green and the use of this slogan cancel in the late 1930s well after the rarer versions you seem to be fishing for.). The perforation rate in the two directions proves an identification with no need to measure the image size at all. 5. Unpause.