The stock shape is similar to a Jezail musket (yes, my dear Holmes- the very gun that gave Doctor Watson the wound that ended his military career) These were Arabic in origin- Afghani comes to mind. Many were made by rather crude cottage gunmakers. Whether yours is an original Jezail, or a bit of a tourist souvenir from years past, I could not hazard a guess. However, if you are in London, there are some museums there that COULD offer you an educated opinion. It is either a very crude matchlock type OR is missing parts- the true Jezail was, IIRC, a flintlock.