At Francisco Fort, La Veta.

First, it's not English made.  The crescent shaped iron buttplate and triggerguard along with the grease hole shout Iron Mounted Southern Rifle.  The lock is off a P-53 Enfield.  Unfortunately, its mainspring broke a long time ago.  It has one brass thimble with no entry thimble and no nose piece.  The barrel is sub 40 caliber and is marked W. Pennebaker, a barrel maker from PA.  I think the lock was salvaged off the battlefield and the barrel a cast off (it's bored off center).

Besides photographing it, it was disassembled.  Water with non-petroleum based vegetable soap was used to wet cotton rags that were then rubbed against the stock to remove the mold (or whatever that white stuff is) and dirt/grease.  Lo!  Beneath that almost black tar was a  walnut stock.  More rubbing brought out the sheen in the stock.  Will post pictures when the director forwards them to me.