Resonator mandolin

The resonator mandolin was developed by John Dopyera, who sought to produce a guitar that would have sufficient volume to be heard alongside brass and reed instruments.

In 1929, Dopyera left National to form the Dobro Manufacturing Company with his brothers Rudy, Emile, Robert and Louis, Dobro being a contraction of "Dopyera Brothers" and coincidentally meaning "good" in their native Slovak language.

Dobro Manufacturing Company licensed designs and supplied trademarks and parts to a series of vendors such as Kay-Kraft, Harmony (Sears) and Regal.

Blue Comet is an inexpensive 1930s brand of mandolin manufactured by the Regal Musical Instrument Company in Chicago, Il that featured an extra wooden sound chamber encircling the body.

Somewhat resembling a banjo tone ring, this chamber contained several small soundholes with metal screen covers.

While the sound chamber may indeed affect the tone or volume of the mandolin, Blue Comets do not contain resonator cones and are not truly resophonic.

In 1938 and 1939, National made a limited number of "Silvo" electrics using the same triangular metal body as the Style 1 resophonic mandolin.