In the late 1980s my grandfather and I found this strange stone on his property in Pike County, Ohio. We wrote a letter to the Ohio Historical Society and included some photos, but they were unable to identify it. It has been in a closet at my father's house since then.

Here's the stone from one side. I included the pencil for scale. You can see that the center part of the stone is rounded and sticks out higher than the "rim" that surrounds it.

Here's the other profile of the stone. We found it near the point where a trail crosses a creek in an area that hasn't been inhabited in at least a century. The trail might have been used by wagons in the 19th century, but now it's only visited by ATVs and hikers.

This close-up photo shows the edge of the rim that surrounds the smooth part of the stone. We can't explain the dark strip along the inner edge of the rim. Maybe it was caused by some sort of stone cutting device. There's a layer of light brown sediment in the gap between the rim and the round part, but we don't know what it is made of or how deep it is.

A shot from above the stone. The markings on the rounded section might be deliberate, but we presume that they are not.