comments:
Error-InvalidName posted on r/artifacts3w
Definitely looks like a river rock worn into a shape for a purpose, just when that was done is the big question. At first it looked exactly like the puck style sharpeners for lawn tools and equipment like in the link below. Which could then mean it could be what was used to sharpen tools used long ago. Really cool find, if you are still there i'd be searching for more items to possibly support the older theory. https://www.amazon.com/Lansky-Puck-Multi-Purpose-Sharpener-Blade/dp/B000B8FW0Y