I'd like to see the extractor arrangement (for pinfires didn't need them) and top of the breech end of the barrels for dovetailed fillers, but those hammers and apparently retro-fitted or removeable centrefire pins scream original pinfire or dual ignition and subsequent centrefire conversion to me; but then the fences look originally purpose-built.
My money's on original dual ignition, subsequently rendered permananent centrefire from that era; I haven't got my refs to hand to see what the patents might be for.
Beautiful gun.