This is a slide-rule base-mounted dial pointer (part #122638-1). It features a 1 1/8" x 3/4" rectangular drive-mounting base designed to attach to a slider track, tuning cord, or drive cable, extending a short 1 1/4-inch indicator needle across slide-rule glass dial scales. This style was commonly used in tabletop radios and receiver units manufactured by companies like Philco, Zenith, RCA Victor, General Electric, and Crosley.