Hi Scott,
No, I don't see any "J" mark but maybe that is how J Resor signed his guns. It looks to me like it might have been converted back to flint using a Siler pan and frizzen . It is a beautiful gun and I while it has wear, scratches, and dings from use, it also looks like you can still see some of the tool marks from rasps and files used to make it.
dave