It does appear to be the barreled set from some type of swivel breech. If it were mine I would give it a good soak in something like a citrus based gun solvent, in the hopes of chemically removing as much of the rust and scale as possible. Maybe then followed by scrubbing them down with 00 or 000 steel wool, in the hopes of possibly finding what remains of any possible barrel markings remaining anywhere. It’s not like you have any finish to protect, and total immersion will also chemically clean what is left of the bores. Then go after cleaning up the bores to the fullest extent possible. I make no claims as to being any type of authority on swivel breechs, I’ve just researched them extensively in the last 18 months, while waiting for my own swivel breech rifle to be built. They are rather rare and uncommon...but have certainly been around since originating in 17th century Europe. I’ve got a couple of friends (including the builder of my rifle, David Price...building them for over 40 years) that are truly much more knowledgeable than I on all things swivel breech...that I will pass this on to. I can’t decide if those percussion drums look to be an afterthought (as in converted from a flintlock), or are original to the build. I’m curious...have you weighed the barrels? I’m thinking them to be fairly light, as thin walled as the lower smoothbore tube is. Am I seeing front and rear sights on both tubes and how are they affixed to the tubes? How do the barrels appear to be joined (silver solder maybe) and how are the ramrod barrels affixed as well? What is there as far as holes through the area between the tubes? Now you’ve got me curious as to just what the heck you’ve got there too, dpw21562??? If you don’t mind, what did you give for the barrels, and what exactly were you told by the seller?