How do you identify maker of Italian black powder pistol?

It can be a monumental task if there isn't a obvious makers name stamped. Many companies imported Flli Pietta, Uberti, Pedersoli and others under US store names often with no makers mark on the gun, same goes for the kit guns. Look on the side of the gun or under the barrel or under the lock plate for any clues. Other than that I would look to the on line auctions like gun broker or auction arms, and see if you can spot your gun in there listings.