Gibson's "own" ES-150, a "more-upmarket ES model" compared to the Ward and Spiegel models, had minor changes from the contract models, such as a solid carved spruce top, maple back and sides, and an adjustable truss rod. They shipped the first guitar to Bailey's House of Music on November 20, 1936. The instrument sold for $155 including cord, six-tube amplifier, and case. The pickup placement, closer to the instrument's neck than on Gibson's EH steel guitars and on guitars made by other manufacturers, produced a warmer, less "trebly" tone that was favorably received by jazz and blues players. In 1937, the model's peak year, Gibson shipped an average of forty guitars a month. In early 1937, Gibson began shipping two four-string versions: a tenor guitar (the EST-150, with a 23" scale, renamed the ETG-150 in 1940) and a plectrum version (the EPG-150, with a 27" scale). Early players included Eddie Durham, Floyd Smith and, the most famous of them, Charlie Christian, who bought an ES-150 in 1936. His joining the Benny Goodman Sextet in August 1939 gave the ES-150 "a near-mythical status" (aided by a feature in that year's December issue of "Down Beat").