Got this for a dollar with the nice bowl/pot from my other thread. Again I am stumped but suspect it is... something.
Very dense, old-looking, seemingly mineral or metal in origin (can't find my testing magnets so will test metallic content once I pick up new ones). The groove in the center seems deliberate, accommodates a finger nicely.
It was surrounded by good items so I suspect something interesting if not valuable, but don't even know where to start researching.