Rich I don't know for certain on the guard, but the previous owner had told me that he believed the guard *may* have been a replacement. I don't know if he ever took it apart. There is a splice or repair joint just forward of the bow on the forward finial, a very clean square-across joint, so ***my guess*** is that the gun originally had a typical decorative fowler type guard that was damaged, and the guard on it now is a composite or repair. I suspect the original buttplate, original guard and side plate all were a suite either purchased or salvaged; I also think the original buttplate finial was probably long and decorative and this abominable repair was basically slapped on to cover up a damaged long upper finial.
The lock itself has had work done to it as it stands, possibly a reconversion. The mortise under it is completely hogged out (very old, not recently) so it's kind of tough to tell if it's the original lock or lock plate. Don't remember what the owner thought at the time but the lock bolts sure are replacements.
Was just checking through photos, the date scratched under the cheek is "1774." Seems a bit early for the gun, although not outrageously so.