Possibly one of the many Belgium guns imported into England and proofed in Birmingham? Or fake proof marks that the English trade had such serious problems with. Not a high quality gun IMO. Figure on barrels may be fake, applied with acid soaked thread wrapped around plain iron barrel that may have been drawn in a rolling mill from a short blank, similar to how musket barrels were made in the 1860's. All this is just a guess and I'll be equally interested in others comments.

John McCain is my war hero.