Paul Bigsby
Famous for his pedal steels and tremolo bars, Bigsby built Merle Travis' electric guitar, and began building electric mandolins as early as 1949. His clients included Eschol Cosby, Paul Buskirk, and Tiny Moore.
     Seven Bigsby e-mandos are known to exist:

These instruments are semi-hollow rather than completely solid; they have a neck-through design with hollow wings. Bigsby also made three doubleneck guitars with mandolin necks, for George Johnston (1956), J.B. Thomas (1956), and Grady Martin (1952), pictured above.