I've had some success reading the (quite small) patent numbers from web images and old Curtis Earl halftone photos, but more often than not the focus and resolution of the magnified images are just too poor to do anything but guess.
The Model 1928 lists 13 patent numbers on the right rear of the receiver (as opposed to just patent dates on other models). I've managed to decipher or lucky-guess ten of them, but the remaining three are just too blurred. This is what I've got so far:
U.S. PATENTS
1,131,319 1,352,414
1,33*,*** 1,357,208
1,340,891 1,363,809
1,340,943 1,403,623
1,347,754 1,4**,***
1,349,345 1,4**,***
1,817,321
Would some kind '28 owner have a look and fill in the blanks for me?

I'm also interested in other Thompson-related patents - whether for drums, box magazines, compensators, sights or the like that anyone can provide. Of course if someone already has this kind of comprehensive list that would be even better!
If anyone's interested, I'll make PDFs available when the job is done if I can find a place that'll host them (wink wink).

Thanks in advance.
Bob