I have a small round metal piece 3/4 of a inch wide and about a half inch thick. It has a slot cut just half way thru it and has a set screw. Kinda looks like Pac-Man. Sorry can't do a picture. Maybe some kind of a adjustable stop ?
EvilDr235

Is the outside polished? might be a hole go/nogo measuring device (set screw calibrates it)....just a wild guess without a pic tho. no hole in the middle?

No it's not any kind of measuring device. It looks like something you would clamp on something to limit travel. Some kind of a stop.

EvilDr235

 I think you are describing a "mini" G clamp, for sheet metal work, is the set screw off centre? I remember making some mini clamps using 1/2" pieces of 3/4" square bar.
Graeme

The set screw is a little off center and it has a straight slot for the screwdriver. The item was with a socket set i bought.

EvilDr235