I don't want to be too commercial here, so I'm sending this to Jeremy only.
Try to pick up my book, BERKS COUNTY LONG RIFLES & GUN MAKERS, published in 2009 as a part of the long rifle exhibit in Reading in 2009. I say that because I address the question of that particular design of engraving on the patchbox as used by at least 3-4 gunsmiths in the Upper Berks county area. Both Jacob George , and Carl George, along with Stophel Long and Gideon Angstadt (all in the book) used that curly thang in the middle and some used the same border engraving. In the book you will see at least two rifles using that engraving and on my Gideon Angstadt you will see the 4 point star in circle design on the cheekside, along with the patchbox engraving. But given all the other features of your gun it is a tough call...could be by anyone of those gunsmiths.
If you cant find the book, email me at eastind @hughes.net-- I have some copies at $75.00 includes shipping in USA.