Huvius,I can give you some info from your pictures.

Original barrels are marked with Sharps roll stamp,either Hartford or Bridgeport,front sight is not by Sharps.

A Hartford collar is a wide groove, cut in the barrel, in front of the reciever. You do have a Hartford style forend,if the serial no. on the forend matches the reciever it could very well have been used in the buffalo hunts. The Hartford rifles were earlier than the Bridgeport models and saw the most use.

Most of the rifles used on the frontier had a rough life, broken stocks etc.......

You can get a letter to see who,when,and where the rifle was shipped to by the factory.