Parts would almost certainly have to be made. Age is hard to determine on French guns, except on a very approximate basis. Safe load would depend on the proof level, but it would not be a good idea to shoot standard, 2 3/4" American 16ga shells in it. If you can take a photo of the barrel flats (area underneath the chambers with the barrels removed) or, failing that, list all the words and marks you find there, we can probably help a bit more.