Some of these old rifles have suffered alterations, making it harder to identify them. In this rifle's case, I think there is a good chance the patchbox is a later addition to an originally plain rifle. I base this on the non-standard 3 segment hinge, the odd shape of the finial, wider than expected lid, and the total lack of dark staining in the wood immediately around the patchbox, from the metal (brass) oxides being rubbed off into the wood over many years. The triggers also look rather later than the rifle, if they are original.
I would hazard a guess that the lock is a poor reconversion of a percussion lock lock plate to appear as a flintlock. Most reconversion parts look to be of newer manufacture, and there is a mismatch in style between the plate and the cock. With that said, it's difficult to draw any solid conclusions about this rifle. Even the trigger guard does not show the expected black inside surface from years of oxidation, making the guard suspect as possibly of newer manufacture until more closely inspected to verify its age and correctness to the gun.
I cannot see where the rear sight sits, so cannot tell if the barrel has been shortened. If it sits well behind the rear sight, then perhaps the barrel has been significantly shortened during its working life. When alterations have occured, it becomes imperative to inspect the rifle hands-on, so that any and all alterations can be determined before making an assessment of origin and age. That is probably the case with this particular rifle. The stock does have a couple of distinctive details. It appears to have a longer than normal wrist, and the top of the comb appears to be flattened, so there are some clues to begin with. But a lot of other questions exist about the gun before any definitive answer is possible. Perhaps more complete photos could shed additional light on this gun, including close-ups of butt plate, toe plate, rear sight, muzzle, barrel wedges or pins, rear ramrod pipe, etc. to give us a few more clues as to its original configuration, and when & where it was made. Hope this helps. Shelby Gallien