Dweber49 - From my view, the most unique and iconic folk art rifles that I have ever seen came out of Kutztown and nearby Rockland Township. All of the other gunmaking “schools” seemed to follow a more formalized craft and style, with decoration much more like furniture decoration of the period.
If I recall, the only gunmakers in downtown Kutztown before 1815 or so included Neff, who was an early maker, Adam Angstadt (the “elder”), and Adam’s son Joseph Angstadt. Neff would have been a contemporary of Adam Angstadt. Joseph Angstadt was noted in Neff’s estate documents, so they likely knew each other - and perhaps the three men worked together. In addition to being a gunmaker, I believe that Neff was a stone mason also. Some of those guys did other work in the winter months like gunmaking.
I am sure that you are correct, that other rifles by Neff exist. Neff must have made rifles from an early period. Some of his earlier pieces may be indistinguishable from some of the early Angstadt pieces. I would need to dig out my notes, to be sure but I believe Neff’s estate documents in 1810 also mentioned a pistol.
There seemed to be a time, probably 1790 or before, when the Angstadt’s and Neff must have transitioned into this high level of folk art. Or perhaps their early gun styles were just as wild. Guns from that vicinity, with that folk art style are fantastic and deserve alot more study. Hope that helps but I did not really answer your question.