poprivit-

Get some photos of the breech end of those barrels.
I'll put them up in this thread along with what we have here.

I don't see any 'major problem' here at all.
I've seen other hermaphrodite guns in the past, this one looks to be in good shape.

If the rim recess is right for modern central fire shotshells, don't bother with pinfire - unless you're just itching for a project.
It looks like (if it really is tight on the face) it'd handle mild black powder loads.
I wouldn't try to run big hot modern nitro-power buckshot cartridges through it -- and if it were mine I'd likely have the tubes X-Rayed before I ran it at all.

Cheers
Tinker