Further to my last post I wondered if your rifle has any government inspector cartouches on the left side of the stock at the wrist. Mine has 2 albeit faint, as seen in the photo. I think most, if not all, of these late NM 1863 rifles had a patchbox whereas the carbines didn't. Very nice example, I do agree with gary that it would be a good idea to carefully remove the surface rust.
View attachment 583701
View attachment 583702