I don't believe that the lock is original to this piece and presents as a 'distraction,' if you will, I submit that the original lock had a small 'tit' or 'tail' that would more properly fit the lock recess.
There are so many repeating elements on this piece, lock panels, portions of raised and incised carving behind the cheek piece or entry pipe, that can be identified on this piece and attributed to known makers. I was going to throw out Jacob Ferree (or one of the Ferre family) as a possible influence (??)... but that stepped toe?
The incised carving incorporated in the 'C' scroll (to the immediate rear of the cheek piece,) which rolls-out and away from the scroll and returns to it, creating, but not making, two (2) opposing complete circles at ~9 & 3 o'clock, is so very unusual, in my mind's-eye.
An unknown apprentice influenced by more than one Master and this piece built as his Journeyman's piece?? Representative elements, but no adherence to a particular/recognized 'school.'
There is something in this family's early history that bears some investigation and it just might provide a real clue: possibly even an advance in our knowledge of interactions between the various gunsmiths in PA.
Actually, I think I'm right back where I started. What does that mean...??