|Rickenbacker Electro-Spanish Ken Roberts Model|
|Period||(1931-1936 production) Official Release 1935|
|Body type||Hollow, Semi-hollow|
|Neck joint||Set neck|
|Scale||25" First Full Scale Electric in History|
|Body||Mahogany (with binding)|
|Neck||Usually Mahogany or Maple(with binding)|
|Bridge||Vib-Rola patented by Clayton Doc Kauffman|
Manufactured by Rickenbacker, the Electro-Spanish Ken Roberts is considered the pioneering "grandfather" to the modern electric guitar as it was the first commercially produced full, twenty-five inch scale electric guitar ever made.  The Electro-Spanish Ken Roberts holds the current world record for the highest price paid for a guitar, after selling in 2017 for $7.5 million. 
Produced between 1931-1936, the instrument line was officially released in 1935 and was terminated in 1937. It is estimated that less than 50 total quantity were produced & sold between 1931-1937. Less than 10 are known to survive today.  It was the first model of its kind to offer players an extended neck that joined the body at the 17th fret, enabling extended playability on the 22 fret neck; a design element that persists in the current day electric guitar. Another key element found on the Electro-Spanish Ken Roberts, was the stock equipped hand operated "Vib-rola" vibrato device produced by patent holder Clayton Doc Kauffman.
The Electro-Spanish Ken Roberts was revolutionary for its time and several of its design elements were cutting edge and exclusive to the model, setting precedence for future electric guitar development into the 1940s and 1950s.  Prior to the Ken Roberts release, lap-steel electrified instruments were played by placing the instrument on the lap of the player. The Electro-Spanish Ken Roberts was designed to play standing up, vertical, with a strap as practiced in modern electric guitar performance. Historians attribute the Electro-Spanish Ken Roberts cutting-edge design elements to its unfortunate negative acceptance by the public, ultimately leading to its commercial termination.
Both the "Electro-Spanish Ken Roberts" and "Electro-Spanish Model B" set the stage for solid body guitar to develop; including the notable Fender Stratocaster and Les Paul whose electric solid-body would reach mainstream notoriety in 1952, produced by Gibson Guitar Corporation.
Dan Orkin, Director of Content with Reverb.com stated in 2017: "What makes this guitar special is that it is what most people consider the first modern electric guitar. There's a lot of debate about which was truly the first one of course. This was the popular guitar music of the time. Electric guitars like this, the Spanish style, really took off with jazz and a lot of the big band music of the time. You had the Vib-Rola system, designed by Doc Kauffman, who went on to collaborate with Leo Fender, and a body produced by Harmony, which was another big instrument manufacturer of the time. So this guitar was a really unique piece of guitar history. Only around 50 of these guitars were produced, and six or seven are known to exist today." 
In 2014, a popular vintage instrument boutique in New York City's Brooklyn neighborhood, RetroFret Vintage Rare & Unusual Fretted Instruments, composed a historical evaluation on a surviving Electro-Spanish Ken Roberts guitar. RetroFret stated: "Rickenbacker were the undisputed pioneers in the commercialization of the electric guitar, and the early Ken Roberts electric Spanish model is one of the most important, if relatively unknown, of their early creations. Although mostly forgotten by history, the Ken Roberts represents a fascinating and important step in the evolution of the modern electric guitar." 
Historian and author Rich Maloof stated in his 2017 article titled "Who Really Invented the Electric Guitar"featured on Reverb.com: "With less than 50 built, the Ken Roberts guitar was, in many ways, the first modern electric Spanish-style guitar ever produced."