The bad news is you haven't hit the jackpot on value on your old gun. The good news is it is likely a pretty good old shooter.
It is a generic French boxlock, built post 1900, as it was proofed with smokeless powder T, that came into use at that time. The chambers are about 2 1/2, they can be safely lengthened, usually, or you can just use short ammunition. Since these guns tend to be light, light loads help reduce the pounding on old wood, and your shoulder. I'll bet it's choked tight (most French doubles are) but, that can be changed also.
These seem to run $250-$600 or so, just good solid old guns for upland use. If it fits you, keep it, and go hunting. If it doesn't fit you, you can have the stock bent or extended/shortened, depending on your needs, and still go hunting.
I don't know who built it, and if it was mine, I might not care. I haven't seen a French double that hasn't been up to snuff yet, if it was used as intended, typically light upland use with more walking, then shooting, on the docket.
Do enjoy it. I know I would.
Best,
Ted
