I live in the piedmont as well. The piece that you have looks like an unfinished discoidal to me. The perfect biscuit shape eliminates nutting stone, for me. The discoids that I have seen here are polished really nice and can be concave on one face, both, or totally flat. They show no evidence of pounding or rubbing, no matter of the style. The nicest ones I have seen were made of jasper. All your piece is missing is a polish and a better uniformed cup in the center. I think unfinished discoidal! Nice find!