Akai MX73 MIDI Controller Keyboard SN 11125-01293

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via this auction

Note the MX73, not AX73.

The listing states it's an analog synth, but according to this other listing on Reverb it's actually a MIDI controller:

"This vintage MIDI controller was released in 1986 alongside the AX73 analog synthesizer as part of Akai's professional series. The MX73 has a six-octave, semi-weighted keyboard with a simple, intuitive interface and an adjustable backlit display. It has 4 zones, 8 programmable controllers (4 sliders & 4 switches) along with pitch bend & mod wheels. "

Update: looks like I actually had one posted back in 2014.