I've only recently started enjoying looking at 19th century patents. I try to find the original patent and then read through it including the drawings...if I have a hard time understanding something I send it to my mechanical engineering professor brother. Reimey, Steve, Toby...and a bunch of others on this board are much more knowledgeable.
But I think you'll need to post the patent number...not just the use number. With the patent number, a determination can be made. Here are 3 fore-end fasteners from the 1872-73 era from my simplified database:
1872 - Anson patent 3791 - fore-end fasteners
1873 - Deeley patent 1422 - fore-end fastener
1873 - Scott patent 615 - “key” fore-end fastener
