Arbiter Add-A-Sound Octave Generator (Frank Zappa etc)

We'll often mention the rarity of particular pieces of gear, but I'm not sure they get much more rare than this! We can't find many examples out there of sold ones, in the wild.

The Arbiter Add-A-Sound is an early analog octave device, similar to an Electro Harmonix Octave Multiplexer in sound and function. You get individual mix controls for high and low octaves, and your dry signal. The octaves don't track like a clean modern digital octave, but instead have a glitchy, synth like tone, with a thick fuzzy quality.

Perhaps the most famous user of one of these is Frank Zappa. See pics for proof! 

Works great, and relatively good condition for its age!