Magnatone amplifiers 1937-1971.
The Magnatone name was owned at various times by Magna Electronics Company, Magna Electronics Inc, Estey Electronics and the Estey Musical Instrument Corporation. [Source: Brad’s Page of Steel]
Magnatone schematics (from Dredge Tone Internet Archive)
Images Magnatone Varsity amp by Magna Electronics Company. circa 1955 Los Angeles California eBay:
Images Magnatone Custom 260 by Magna Electonics Inc (circa 1959)
Image 1962 Magnatone by Estey Electronics Inc, Torrance California
Image Magnatone Estey Electronics Inc, Hicksville New York amp eBay: Circa mid 1960s