Can anyone identify this tool for me
It's a floor jack height extender.

Wow! I really love all the comments. The ones I'm actually familiar with had knurling on the sides instead of the black, looks like abrasive, coating shown on this one. They came in three different sizes and the set included a jack with a hole in the lifting plate that one end of the height increaser would fit into and a flange that would fit over the top for more stability. We mostly used them for support when working under machinery that had been partially lifted as they were easy to operate in confined areas without that 12" handle that's on many other types of supports.

Do you have any other parts like I've described?