Have they the weight of a rock or are they on the light side?
Cool looking for sure-kind of look like a seed/nut of sorts.
If I didn't see you holding them and saw a picture as this-old rusted up bed pan comes to mind.
I find those kind of rocks in small brook streams. They are not that rare. If I remember correctly, the hole in the rock was a softer mineral and washed out over the years from the river current. Someone out there knows for