I have a London armoury 3 band musket that has been in family since 1946.I recently got it out with the idea of shooting it. while I had it disassembled I discovered that it has no serial number. It is marked on the lock, barrel, stock and screws with the roman numerals XIII or IIIX could this be a prototype model (#13 or 7) ? The history on this rifle is that my father bought this rifle from a man who said his father carried it in the civil war. Any info on this rifle would be greatly appreciated. thanks