As you can see from the pictures here, there were two flavors of this amp out there, the Silvertone branded model and one with a Harmony brand. Danelectro wasn't fully on the scene yet, and Lectrolab was probably more than happy to job these amps out to the biggest department store and catalog sales institution in the world at the time.

As was common for many Sears-offered products, the Silvertone brand was applied to another manufacturers' product. This was true of literally thousands of products from 1916-1972.