Ok, it has McCormick Deering (sp?) cast into it. it is designed to clamp on to a (bar?) of some type. The diamond shaped grinding wheel moves up and down while spinning around. So what is it? Or more accurately what dose it sharpen? And lastly what is it worth?

It's a  grinder sharpener for sickle bar knife sections for mowers, binders, etc. It was made to be clamped to the iron wheel of the implement when used. I would say $35 to $50 would be the price range.

I got lots of parts for sickle grinders, mostly ih and related companies, no stones though.
thanks.