The lock does closely resemble a 1746 French musket (the only one without a bridle), but there are a couple differences in the proportion of the tail and the frizzen spring finale which make me think that this one didn't come out of a French arsenal. Might be a sub-contractor's work (I don't know how the French musket-building system worked, particularly for the 1746 musket, which was something of a simplified emergency model I believe) and the frizzen spring and top jaw screw could easily have been replaced at some point, but it could just as easily be a French, Dutch, or German commercial lock made in the same style.
The buttplate could also be musket plate reworked for a flat toe - hard to tell without better pictures, but the shape of the triggerguard behind the trigger looks like it was formed from sheet metal and is not a recycled musket guard.
I hesitate to bring this up, because the siren call of the "Early Southern Iron Mounted Rifle" is strong and I don't know how significant it really is, but the shape and proportions of the stock are virtually identical to another iron-mounted rifle, also with a flat buttplate, which is illustrated as rifle 3 in Gusler's March 2004 article in Muzzleblasts and is itself strongly reminiscent of the "Old Holston Rifle." I doubt that this one is by the same hand, as the workmanship is much nicer on this one, but the resemblance is intriguing.
