A vintage (and seemingly mint condition) Westinghouse type ST-35 Ammeter, Style PH-40151-3 with a rating of 0-10 Amps. Not sure on its exact age, but the logo on the bottom was in use from 1936-1960, and judging from the style of the sticker on other ammeters of the same make and model on this job, we'd estimate it's probably closer to the older end of that range, possibly a surplus from war effort production. Seems to have been intended for use with radios somehow.