United States Stamps From 551 To 574

This is my first post about stamps. I hope you like it and can help me.
The stamps are numbered from 551 to 574. I'd like to know if the numbering is correct; I bought them about seven months ago.
Thank you.

Hello and welcome.

The 551-573 set from 1922-1925 is "perf 11x11" meaning that there are 11 perforations every 2 centimeters, both horizontally and vertically.

The same stamp designs were printed again from 1926-1934 using a different printing mechanism (rotary press instead of flat press) and those perforations measure 11x10.5, that is 11 perforations every 2 centimeters on the top and bottom, and ten-and-a-half perforations every 2 centimeters on the sides.

It is very hard to count the number of perforations by hand to that degree of accuracy, so using a perforation gauge is the easiest. If you don't have one, you can buy one on the Internet, or even download one and print it out on your own printer.

Without a perforation gauge, for this particular set, you can easily take one of the stamps off the page and compare the perforations with the other stamps. If they are all perforated 11, then all the perforations should match all the other stamps on all sides.

Here is an example, I took the 1 cent from your picture and rotated it to compare the top row of perforations to the side perforations. If 11x11, the holes should line up exactly. But in this example they do not. The holes align at one end, but by the other end they are not aligned. Because of this, I predict that the 1 cent stamp is not a #552 perf 11x11 but is instead a #632 perf 11x10.5 from the later series. (I picked that stamp because also the color does not look like the typical dark green of #552 but more like the yellow green of #632, but there were many shades of color for the different stamps of this series so measuring the perforations is the primary method of identification).


Summary:
Perf 11x11 -- Scott #551-573
Perf 11x10.5 -- Scott 632-642 plus 692-701
Perf 10x10 -- Scott 581-591
There are also coil and imperforate and other variations, but these are the 3 basic sets of this stamp.

The one dollar denomination was only made as perf 11x11 so that is a good example to use for the above perf comparison test. (The $2 and $5 were only perf 11x11 as well, but those are more expensive stamps so I wouldn't recommend rough handling them for this perforation comparison, but the $1 is very common and easy to replace if you manage to damage it).

Enjoy!

After using several Perf gauges, you will get to where you can tell a 10 perf just by looking. It's much like recognizing the teeth on saw blades for wood or metal. Or my eyes get blurry and I pull out the perf gauges to confirm. The clear ones are handy for measuring frame to identify flat vs rotary as well.
Our club usually get several donated a year and we offer them to members for free. Always good to have a club nearby.

Most of the stamps appear to be rotary press stamps, Scott 653 (1/2 cent) and 632-642 (1 to 10 cent). Rotary press stamps printed after 1930 display brighter colors than earlier rotary press stamps or flat plate stamps. Vertical (portrait orientation) rotary press stamps are slightly taller that flat plate stamps. The $1, $2, and $5 stamps were printed were flat plate only and are the only stamps in the image that are for sure correctly identified. Any of those three stamps can be used to check the perforations on the other stamps. If the perforations do not match end to end, the stamps are rotary press. Also, a 1 cent 632 covers the spot reserved for a 1 1/2 cent Harding (profile view) stamp. Some of the other 11 cent to 50 cent stamps may be flat plate.

Flat plate stamps are likely to have flecks of ink adhering to the back of the stamps, called "setoff". acquired from stacking sheets of stamps to dry after printing and before gum was applied. Rotary press stamps generally do not have ink flecks on the back. Gum was applied by the rotary press immediately after printing.

Excellent information. If you can, I'll post another sheet I bought today or tomorrow, covering pages 575 to 596, to get your opinion. Thank you very much.

Before you do that, please check the perforation rate on those as described in the various posts above. We want to see if you understand the differences in those series.