I am looking for information and value of a J. Stevens Tip-up shotgun in great condition for it's age. I think it is a 14 gauge (12ga will not fit and 16ga to lose) and it has a patent date of 1864 on it.
Your gun should not have a forearm stock, and 14ga is correct for the Stevens tip up. This is a rare piece due to the chambering (the Blue Book does not even list it) and you should (IMHO) have it appraised by a professional.