Hey Reaper,
Did you see the article in the Ohio Ach. Journal a while back about nutting stones?
The guys theory was they were used for dressing antlers for flint knapping. He knaps, and dressing his antler on sandstone created cups, once they were too deep he would have to start another cup.
It makes sense to me, i could never imagine laying a few nust in some cups to crush them, they were eating chestnuts anyway, which aren't going to roll around.
I have found some with cups on all sides, and not very flat.
what do you think?