I guess if I were in your situation, I'd take it to a competent gunsmith for an evaluation. He should be able to tell you what you have and what he feels about the quality of the piece. You probably can get a good idea of caliber just by looking at the bore, but as far as to what it's chambered for, best get some professional help, IMO. Funny, most 'smiths stamp the barrel as to what it's chambered for when rebarreling, if indeed that's really what you have.