In Bivins notes on the second edition, he added a brief note that acknowledges a possible Virginia origin on the assumption that Thomas Cellars was the maker. I believe the rifle actually came out of the Cellars family in Ohio a long time ago, and has traditionally been associated with Thomas Cellars. I am not extremely familiar with Cellars, but believe he came from Maryland and then perhaps worked in Virginia(?) and the family eventually ended up in Ohio. The gun is a brass mounted gun. So with regard to your project, I guess it would depend on your goal - I do not know if this gun is definitively attributed to Virginia, North Carolina or some other location at this point. Mel notes that it looks to be by the same hand as another early piece in Shumway as well. It is a great gun regardless of where it was made.
The box design is a great example of how Hershel developed his own spin on documented elements that he incorporates and morphs into his own artistic interpretation. He has built a number of rifles with variations on that patchbox - the ones I have seen he made up in iron, but always varied the shape and scale of the box to fit the gun.
There is a commercially available version of that patchbox but I feel it is a bit mis-shapen and much too big. It can be used for a nice look, but recommend cutting off a whole hinge knuckle on each side on both sets of hinges, reshape it a bit, and I like the look of the original with 4 screws better than the 2 screws that come with it.
Best regards
Guy