James-I,
There's a good chance a serial number is stamped on the underside of the barrel (covered by the stock). If you (or someone experienced with such arms) can push
the wedge/key and free the barrel - I can most likely provide some historical information - if there is a serial number.
I'm assuming it's a hooked breech gun. If not, the tang screw would have to be removed.
Only someone with the proper fitting screw drivers (hollow ground) and knowledge should do that.
It has a late-1830s to early 1850s look.
The barrel finish is what Rigby called "pickled" - it's an acid etching process. You should be able to 'feel' the Damascus pattern of the barrel.
