one of dem hard to figure deals to me. :confused:
kinda small to be a grinding stone ... and although it could be, just don't look like a hammerstone to me.
Were there flakes and debitage where it was found? Sometimes looking closely at everything at a spot will clue tool type/usage.
Top of the hill likely was not the top of the hill 15,000 years ago either.
The again, someone may have had it in their pocket cause it looked neat fifty years ago, and decided they'd carried it far enough when they topped that hill.
hope that clarifies things.