Sounds like a Remington Rolling Block.
Remington made millions of them in several different sizes to handle everything from .22 short to .50-70.
I would not pay good money for one in as rough condition as you describe. It would take serious gunsmithing to tighten it up and reline the barrel to make it shoot safely and well. And I don't care about wallhangers. But you said you do, and that is about what it sounds like.