Cherokee Lawman,
Does the rifle have any legible markings at all on the barrel or the lock? Any markings would be helpful. Bear in mind, however, that the lock and/or barrel may have been mass-produced and purchased as parts by the gunsmith for stocking and assembly into a finished rifle. Barrels marked Remington, for example, were sold all over the country, as were Goulcher locks.
Any oral history or family lore pertaining to the rifle may also be of value. If you could give us an idea of the bore size, that might also be helpful.
I am not an expert, but to me, your rifle has the look of something built in the upper midwest in the mid-19th century. That type of scroll guard was used a lot in that general region, although a number of California-built rifles of the mid-19th century also had them. On the other hand, the absence of a rib under the barrel, with the ramrod pipes attached directly to the lower flat of the barrel, is something I would associate more with the northeast.
One intriguing feature is that acute angle in the "step-off" of the lockplate, just forward of the bolster. We would normally expect a 90 degree angle. However, I have recently seen photos of two supposedly "Hawken" fullstocks that had lockplates just like that. I think those locks were probably mass produced for the gunsmithing trade, but I don't know who made them.
I think it is a nice rifle. It has seen some use and sustained some damage, but it looks as if all of the major parts are present. There are a lot of under-appreciated later-era percussion rifles out there, and I don't think they command a very high price on the market unless they are unequivocally marked by a famous maker or have documentation of ownership by a well-known personality. However, that should not diminish your rifle's value as a family heirloom.
Please look it over carefully and let us know if you find any marks at all, or if you have any family history on this rifle, that might guide us to the maker.
Notchy Bob