SUPERTONE

This trademark has been identified as a House Brand of Sears, Roebuck and Company between 1914 to 1941. Instruments produced by various (probably) Chicago-based manufacturers, especially Harmony (then a Sears subsidiary). Sears used the Supertone trademark on a full range of guitars, lap steels, banjos, mandolins, ukuleles, and amplifiers.
In 1940, then-company president Jay Krause bought Harmony from Sears by acquiring the controlling stock, and continued to expand the company´s production. By 1941, Sears had retired the Supertone trademark in favor of the new Silvertone name. Harmony, though a separate business entity, still sold guitars to Sears for sale under this new brand name (source: Michael Wright, Vintage Guitar Magazine).