This is a very nice clean Screw Thread calculator marked "THE L.S. STARRETT COMPANY ATHOL MASS. U.S.A. PRINTED IN U.S.A." The calculator is two piece, the top section spins, for finding sizes of tap drills for NC and NF, also NPT on the back side. They calculator is printed on a cardboard, or heavy paper with a plastic coating, and the little chart seems to be a thin sheet of plastic material. The calculator has a metal center pivot in good condition. As you can see, there is some age toneing and some staining on the calculator, but all the text is legible. The calculator measures about 2.7" in diameter with a 3" x 4.5" card behind it. We don't see many of these without the copyright date on it, or a newer printing, as the oldest printings did have a 1943 copyright date on them.