It could be Henry Thomas, a Birmingham gunmaker whose dates are appropriate. The real question in my mind are those proof marks which are supposed to be Tower Private Proofs but they don't look right. They look, in fact, like "fake" Tower proofs or that they were stamped with the dies sold by a well know supplier of black powder parts. The pistol looks good but the proofs are highly questionable. I suspect...and this is a guess, that's a better quality pistol made for export. Does it have a known provenance?