I have no idea!  And I'm usually pretty good at figuring these things out. Bought at a re-sale store. Very heavily made, 11X2 inch X 3/8 thick , I think stainless steel. has two scales, both in millimeters. The slide section has a screw for fine adjustment; however, the screw has an interrupted thread to allow disengagement from the "nut" there-by allowing free movement of the slide.  A curious thing is the notation "clean in gasoline weekly" ... so pretty safe to say not a food or medical implement. The only other mark... "Made in USA" and "31662". The one metric scale is engraved in the body of the tool, the other, with the finer graduations, is apparently removable, being held with screws. Perhaps this to allow installation of a different measure scale, imperial perhaps? The configuration hints at some kind of "caliper" measuring tool. Any ideas???

Joe B

I think I have one of those in my extensive measuring tool collection.  I will be ashamed if I do not get it right.  I believe it is a typesetter's tool for holding the print block/type.  I believe you will find that the one scale on the top is probably pica, 1/6 of an inch.

BINGO ! .... thanks, wv, the scale, indeed is 1/6 inch   

Joe B 

Way to go, wvtools! Sounds like you got it.