Pirate special

[andy52]

That was my first thought also. But it seems an odd location for a belt hook. Possibly a separate "loop" of some sort on the belt (?)

Rick

You may be right, it could work somewhat like a frog.

 

[BadDaditood]

So it’s not a real early picatinny rail?

 

[Tanglefoot]

Looks to me like it was intended to be carried thrust into a loop of leather or metal, maybe on a bicycle like the old “bicycle guns” — or in a cross-draw position on a man’s belt under a coat. Might also be a storekeepers pistol, hung on a loop or even a protruding nail under a cash register or in the kneehole of a desk with the flat side of the piece flush against a vertical panel and the butt down.. The large upswept hammer shape suggests it’s intended to be cocked in a hurry, perhaps with the shooter’s weak hand, or even by hooking it with loose clothing. Clearlyt it’s a belly gun, intended for very close range. Might be devastating if loaded with coarse shot and a very unpleasant surprise for a robber with a knife. Anyway, that’s my best guess.

 

[Ferryboatcaptain]

From what I can find on the net it has the look of a box lock