Help With Flat And Rotary Press Stamps

Looking for any words of wisdom or guidance in determing Flat and rotary press millimeters on some of the washington and franklin stamps. I have 2 different guages but hard to determine if they are 22 1/4 or 22 1/2 mm. I know I dont have lots of the rare. But I would like to know of a way to help determine the differences. My eyes are not what they used to be.

Thank you for your time and assistance.

Respectfully,
Richard

Try first by sorting them out by perforations.

Rotary's are always wider. Just line up the edge of the designs so that both stamps are visible.

Rotarys can also have a taller image. But not both.


-IBFS

Some use a cut out template of a flat plate stamp to compare against such as from a low value used perforation 12 W/F stamp. Make sure that it is a stamp that is already damaged and of low catalog value to make a template out of. See the following page: http://www.1847usa.com/FlatPlateVsRotary.htm

You might want to read the post "596 candidate?" further down the page, posted on 6/13/14. Some good insights, maybe? www.1847USA.com and Scott Specialized are good references but not absolutes. In general, flat plates will have ink on the back of the stamp that was transferred from the sheet that it was stacked on because the ink wasn't completely dry on the sheet it was placed on top of. It can vary from a little (or in some cases none) to a lot. Rotary stamps do not have that trait. Many rotary stamp images, to me, look flatter or having less dimension to the image, but that's just how I sometimes see them and by no means a determining factor. Rotary press stamps will be either taller or wider (as mentioned) then flat plates because of the printing process (cylinder plates vs. flat plate) as noted in the two references mentioned above. If you want to spend a few bucks, a Sonic Imagery Labs Precision U.S. Specialty Multi-Gauge is a pretty good tool for measuring the MM. sizes as well as other factors measured.

Flat plate will have a crisper, more defined impression.

Thank you all for the guidance. the articles offered were a great help and I was able to make cut examples to help for future stamps.

Thanks!