There was a US law requiring national origin marking on guns in 1903.
Shows up on early Luger imports; although I don't know if it would apply to a muzzleloader.
1911 and 1939 catalogs on line? Not likely, I got reprints from Cornell.
https://www.cornellpubs.com/index.php
Don't get too excited, the EXACT gun you show is not in either of mine.