20 years ago Red Tully (long time Western KY collector) communicated that he thought these biscuit things were cooking stones. Yours looks very similar to the image in my mind from that discussion.
In first pic I thought maybe a discoidal but I after seeing 2nd pic not sure .... that dimple looks similar to ones on nutting stones but it looks too well made just to be a nutting stone ..... interesting for sure
Cooking stones are heated in a fire then placed in a clay pot with water in it. The heating and quenching eventually cracks the stone. These broken pieces are common on campsites are called "fire cracked rocks". The piece the OP shows is well made. Not likely you'd spend that much time making a item that would be cracked in a fire. I'd go with discoidal myself. Gary