Agree with the assessment that this is an Upper Susq made rifle. Lots of candidates for having built this rifle; several come to mind: Samuel Morrison, one of the Dreisbachs, Levi Kaup, Joseph Long, one of the Baums, or an unknown maker (initials anywhere?). I am sure that I left someone out, here, in this list. But, you get the idea.
Since the stock lacks carving, I am not sure that it qualifies for 'Golden Age' status, but it is clearly a nice piece. The patch box is very fine, as is the quality of work, and the profile.
Thank you for letting us look it over and hope that you put it into the Library.
Dick