Dating valco guitars
For the most part, they have a small metal plate on the back of the neck, on the opposite side of the neck from the nut.
Regal also built resonator guitars using Valco parts, selling them under its own brand.
Then, as now, guitar players wanted to be heard, and that desire drove the development of these resonator guitars and the electric guitars and the amplifiers that would soon follow.
George Beauchamp, one of National’s founders, is credited by some with creating the “Frying Pan,” an electric lap steel guitar, in 1931 with Adolph Rickenbacker.
The Supro brand name was introduced in the mid-30s for cheaper electric instruments. The company was based in Chicago (hence the Chicago 51 postal address that appears on some amps and at this sites home page).
National-Dobro was reorganized into the Valco company in 1942. Manufacturing of resonator guitars ceased with the introduction of metal rationing in World War II, and the focus was placed on Spanish- and Hawaiian-style guitars and amplifiers.