My flinter is not nearly as nice as yours. It is a single barrel, of course, marked Tirebuck on the lock. Was made in London. It still sparks up a storm and because of its pitted condition it wouldn't hurt to shoot it, but I don't trust the barrel. Bore is fine, tho. Has the water proof pan and roller on the frizzon, so it is a pretty advanced design.
It looks like a ten bore. It is quite light and comes up nice. After my life insurance is paid up, I may shoot it. It has what looks like the original ramrod. Someone loved it because it was shot, and the bore is fine, then it was dumped in a basement someplace...for about a century and a half.
It is not so nice from this angle.
Anyone recognize this proof mark?