Finding a Rare Firearm

Wouldn't you love to find a rare firearm? Wouldn't you be excited? How would you prove the provenance on such a thing? How about having the rifle shown in the photo? The owner is Johnse Hatfield, of Hatfield/McCoy feud fame. The rifle is an 1876 Winchester, chambering and serial unknown. I've been in contact with the fellow who thinks he has this jewel but, no, I'm not telling who. I just think it is cool that there are still such things to discover.

Oh, for what its worth I think the image is reversed. Notice the lack of loading gate, with the rifle in this position it will twist to the correct orientation.