old 'pocket' voltmeter electrical tester by STERLING

This little 'pocket size' voltmeter measures about 2-1/4" across its chrome plated case. The red lettering on its face identifies it as made by THE STERLING MFG. CO. CLEVELAND, O. MADE IN U.S.A.". It is also stamped "MADE IN U.S.A." on its backside. Its scale ranges from "0-50 VOLTS", which I presume indicates DC voltage (?) since most typical AC voltage readings (for normal US household current anyway) are more than twice that. Also guessing it is ca. 1950's or so in age (or a little earlier?) due to the fact that the wire lead attached to it (w/original looking probe tip, etc.) is plastic covered instead of cloth.