Just a note that even in the flintlock era, few PA rifles were really "made" by local gunsmiths, if by that you mean the Colonial Williamsburg concept. Most of those rifles were more like modern custom guns, being assembled by gunsmiths from purchased parts. Barrels were available from barrel makers, locks from lock makers, furniture like buttplates and trigger guards were available from specialist casting shops, even stocks were sold in a "semi finished" state.
Very often collectors talk about this or that "school" of gun makers and point to such things as the patch box indicating a certain area. That was partly a matter of apprenticeship or copying, but mainly the result of the gunsmiths of that area buying their patch boxes from the same source.
I am from north of Bedford County (Cambria County) and there were several gunsmiths active in that area, but I have not seen anything much about them. I have a late percussion rifle with straight (yes, that is correct) rifling. No turns. It is pretty much an assembled rifle with a Little barrel and an Elwell lock. Caliber is .45, but the barrel measures an inch across so it is pretty heavy. I suspect it was made for some kind of target shooting, as it is just too heavy for a hunting rifle. I am sure the rifling had to be a special order.
Jim
P.S. A big +1 on John Zimmerman. A real old school gunsmith and a delightful gentleman.
JK