For what its worth, a Manton muzzleloader was what old Pomp Eddins shot in Nash Buckingham's wonderful story "Playhouse", just recently reprinted in the 30th Anniversary Sporting Classics magazine: "Muzzles paper thin. Locks that sang like harp strings...." Pretty high recommendation it seems to me. Good luck.

There were two Manton gunmakers: Joseph (the father) & John (the son) and BOTH were the best of their time. Your gun looks like a "Joseph"

Best Regards, George

A Manton is the Rolls Royce of his time. When I was a kid I used to go to Bond Street in London and look at the fine cased pistols for sale. A cased pair of Manton dueling pistols then cost around $300 and they were just wonderful. This was in the late 50's.

I had a friend who bought a cased set and we used to go out and shoot them! They were flinters and went off instantly. This was a little later, and he paid $3000 for them.
They were like new. We shot the old balls that were in the case. This was in the late 70's. I recall the fantastic brown damascus pattern in the barrels. Just amazing.