As you may already know, you have a modern reproduction longrifle that has a few years on it, so it's getting some patina on it. If the modern maker signed it, you should see a name or initials on top of the barrel several inches behind the rear sight. If not signed, it will be difficult to determine the maker. The initials on the patchbox lid are probably those of the owner... so if the owner was the maker, then perhaps one of the modern builders will recognize the initials. But if the owner purchased the gun, we're back to probably not knowing who built it.
Shelby Gallien