Im thinking strong possibility ,i could be wrong but but both sides makes it seem realistic . looking up close one side looks to be did with hollow cane and other side looks like a solid piece was used.
Id say context is important here ...Was it found close to an area where you have found other artifacts ? May help determine. If I found around me I would think natural , rocks similar to that are common in the rivers here.
Looks like a counter weight to me. Holes almost same spot on both side. Tear drop design. Looks like it was hitting there on the one side to stop the drop. Just a guess but a pretty good one...