It's in many ways a sort of a copy of a Henry Scroll or Late English model (Late model originals were made starting in 1834 and built in Lancaster Cnty, PA) - the patchbox is definitely styled after an Old English model - the late models used either the Old Model box like this one or one of the various styles used on the Henry Lancaster/American Model. The JH on the lock goes along with this theme - Henry's initials were JH
The buttplate is definitely an early (pre-1850) Hawken style. Can't see the guard that well, but looks like a scroll guard? While not a classic Hawken it's well within some of the variant styles on their known rifles like this one:
The lock looks like an L & R See the link for a comparison of a current model:
http://www.trackofthewolf.com/(S(n...4&subId=148&styleId=830&partNum=LOCK-LR-900-D
Hammer's a bit different than the current one but could be an early model or a replacement.
Age - IMO can't be older than the Sharon barrel
FWIW - it's someone's interpretation of either a full-stock iron mounted Henry (originals made from 1830), a generic Rocky Mtn aka Plains rifle of the late 1820's to 1830's - it fits well into this category, or possibly??? an early flint Hawken. I tend towards the Henry interpretation
I'd say it's worth taking a look at and if the barrel (use a bore light) and lock innards are good and the stock shows no damage, then dependent on price IMO it might not be a "bad" piece with a bit of clean up. By the hand wear on the forestock this one has been carried for a while.
Track has innards if it is one of the old L & R Sharon locks:
http://www.trackofthewolf.com/(S(t...subId=147&styleId=802&partNum=LOCK-LR-UPGRADE
Pull the lock and see if there are any marks there...
Here's a link that has links to pics of a fullstock percussion Sharon - guard doesn't match for one...
http://members2.boardhost.com/TradeBlanket/msg/1246934805.html