I say new because likely no one has seen this one before. It is in storage at the Montana Historical Museum and Vic Reiman showed it to me. You Hawken experts will say "That's not a Hawken!" and although I am in no way an expert, it is not like anything I've seen, except there is another like it on the Buffalo Bill Historical Center website. This one had about a 38" barrel. The triggerguard is a little like Track's London style fowler, #TG-Fowl-L-I.
Unusual breech plug.
The long toe plate has a patch box release button.
The patch box has a flower engraved on it (hit Control + to enlarge). The butt plate is 4.5" tall, has a 3" return and a 1.07" belly. Nothing like it in Track's catalog.
Unusual cheek piece and hump in comb line.
What is the inlay for, not an apparent repair.
Long entry pipe. Keys enter from right, ends not notched.
A longer dovetail than on the Bridger Hawken.
Muzzle, relieved for ease of loading.
The owner didn't like buckhorn sights, filed the horns off.
Unusual J&S. Hawken stamp. Appears to have been double-struck and misaligned.