I found this gauge in a tool chest I purchased. It is made by KENT MOORE ORGANIZATION INC JACKSON MI. J - 7316. It measues 4" tall, 6" including the plunger. The plunger moves the flat piece of metal at the bottom downward, then I guess you put whatever you are gauging between that and the round piece, because when you depress the round piece the gauge moves.
I think it is related to automotive work, but those tools are not my A game. Any help would be appreciated. I tried e-bay and google with no luck. Thanks