The Wurlitzer Sideman
The Rudolph Wurlitzer Company (Wurlitzer) released the first commercially produced drum machine called the Sideman in 1959. It was an "electro-mechanical" drum machine that offered a choice of 12 electronically generated predefined rhythm patterns with variable tempos. "The sound source was a series of vacuum tubes which created 10 preset electronic drum sounds. The drum sounds were 'sequenced' by a rotating disc with metal contacts across its face, spaced in a certain pattern to generate parts of a particular rhythm. Combinations of these different sets of rhythms and drum sounds created popular rhythmic patterns of the day, e.g. waltzes, fox trots etc. These combinations were selected by a rotary knob on the top of the Sideman box. The tempo of the patterns was controlled by a slider that increased the speed of rotation of the disc. The Sideman had a panel of 10 buttons for manually triggering drum sounds, and a remote player to control the machine while playing from an organ keyboard. The Sideman was housed in a wooden cabinet that contained the sound generating circuitry, amplifier and speaker." (http://en.wikipedia.org/wiki/Drum_machine)
Controls
Controls
Sideman in Wooden Cabinet
Sideman in Wooden Cabinet

Wurlitzer, was an American company that produced stringed instruments, woodwinds, brass instruments, theatre organs, band organs, orchestrions, electronic organs, electric pianos and jukeboxes. Over time Wurlitzer changed to producing only organs and jukeboxes, but it no longer produces either.