Origin of the gun COULD be English, but as has been mentioned above there have been many locks with fake markings. It is NOT a SNIDER gun as suggested by Teodor. These had side hinged breeches and were not muzzleloaders.
The decoration style (in parts) looks Yemeni, but in fact could have originated anywhere, and may not even be very old as "ageing" is/was very cleverly done to fool the unwary.
A nice piece just the same and I like it very much.
As a note of caution, please check that it is not still loaded......
Stu