I hesitated to jump in on this conversation regarding the stocking originality. However, in my experience examining similar fowlers here in New England, this one is 100%. There is an original fowler, dater 1757 on the thumb piece, that I examined closely about two years ago. It, and it’s maker, had been unidentified. However, I conclusively found its maker, Barnabus Mathis from Marlborough, Mass. (central Massachusetts, where many in this "Frencvh style were made), and added it to several other fowlers made by him (1750s-1760s). He was dead by the early 1770s. So, this newly-seen fowler on this website, while somewhat similar to the example from 1757, is different in some details. This newly found one on the website is also dated 1775 on the thumb piece.
You’ll immediately see similar lines, curly maple stock, etc. The recycled iron stock furniture is similarly French. The iron butt plate, lock (replaced on the 1757 example with a later lock), iron side plate, & trigger guard are similar in form, too. And the stock form is the same. I'd love to see more of this gun "in the flesh" and see or create more photos.
Also, fine curly maple stocks are seen on numbers of New England fowlers by the 1750’s onward. In fact, we New Englanders were putting such fine-grained maple into our long guns a full generation before it is seen on PA long rifles! It may just be that the riflemen who served in the 1775-76 Siege of Boston army, seeing the appearance of such New England fowlers, desired similar treatment on future PA rifles. Now wouldn’t that idea raise the eye brows of many PA long rifle collectors??!!
I am, your humble servant, Rich C