57T200A

Pages 762 and 763 of the Fall 1929 Sears Roebuck catalog lists Silvertone tubes for the first time, with a totally new type number, for example 57T200A = UX200A. Research has not yet provided a manufacturer of these tubes and Tyne's "Saga of the Vacuum Tube", page 362 states: "No information available" for Silvertone. It is presumed that these tubes were made by the Sonatron Tube Company, with an address in Chicago and also in New York and it is also known that Sonatron acquired three smaller companies in 1929, before they, themselves, were acquired by National Union in September 1929 (Tyne page 359). Silvertone tubes continued to be available for some years and tube boxes with both Sears Roebuck and Silvertone printed on them are relatively common in the US. Sears Roebuck Archives state that the company "ended its association" with Silvertone (radios and or tubes is uncertain) in 1972.

For use as a supersensitive detector in amateur receiving sets.