Wheel or Cylinder ID?

[douging]

My boss posted this on Facebook awhile back. I asked several friends and family. No one could identify what this was. Any ideas from this group? It’s been a paperweight at a Chevy dealer service counter for decades.

 

[douging]

Another shot.

 

[Modern Garage]

I suspect it went missing from the special service tools board. I would expect it to have a part number on it, but perhaps not if it was part of another tool or assembly.
Joe

 

[shiftomoto]

Cylinder for a very large pistol? lol