principal partner, Adolph Rickenbacker. During the early production of the A-22 Fry-Pan, Beauchamp and Rickenbacker would experiment with wooden-bodied Spanish guitars and solid body prototypes; ultimately giving birth to the Electro-Spanish Model B and the Electro-Spanish Ken Roberts. Both models had been experimental, produced as early as 1931, and officially released in 1935. The Electro-Spanish Ken Roberts model was subject to a limited production of forty-six. There were several new design elements found on the Electro-Spanish Ken Roberts. The instrument was the first of its kind to be named for an endorser. While most arch-top guitars had 14-fret neck joints, the Electro-Spanish Ken Roberts fingerboard joined the body at the 17th fret allowing much greater access to the higher frets, creating a full 25-1/2" inch scale. This addition made the Electro-Spanish Ken Roberts the first production full-scale (25-1/2") electrified guitar. Another new feature on the Electro-Spanish Ken Roberts is the stock Kauffman Vib-rola tailpiece, the world's first patented tremolo (). The Ken Roberts is the first instrument of any type to feature a hand-operated vibrato as standard equipment. It also marks Rickenbacker's first link to the unit's originator, Clayton Doc Kauffman, who would become a design collaborator for the company a couple of years later. Model B Electric In 1935, the company introduced several new models including the Model "B" Electric Spanish guitar, which is the first known solid-body electric guitar. Because the original aluminum Fry-Pans were susceptible to tuning problems from expansion of the metal under hot performing lights, they made many of the new models from cast Bakelite, an early synthetic plastic used in bowling balls. Rickenbacker continued to specialize in steel guitars well into the 1950s, but with the advent of rock and roll, F.C. Hall, owner of Radio & Television Equipment Co. (Radio-Tel), purchased the Electro String Company from Adolph Rickenbacker in 1953. Hall overhauled the business and began focusing on standard electric and acoustic guitars rather than the steel guitars the company pioneered. In 1956, Rickenbacker introduced two instruments with the "neck through body" construction that became a standard feature of many of the company's products, including the Combo 400 guitar, the model 4000 bass, and, later, the 600 series. Neck Thru consists of a single wooden piece from the neck through the central body section. In 1958, Hall introduced prototype called "capris" (the same name of Hall family's cat from the pronunciation of the