The Roland MKS-20 is a professional-grade 2U rackmount digital piano module released in 1986, based on the RD-1000 stage piano and featuring Roland’s proprietary Structured/Adaptive Synthesis (SAS) engine. It offers 16-voice polyphony, eight distinct timbres (three acoustic piano, two electric piano, harpsichord, vibraphone, clavinet), and built-in stereo chorus, tremolo, and 3-band EQ with sweepable mid-range for deep tone shaping. The SAS system emulates nuanced dynamics by analysing 88-key, 128-velocity-level piano waveforms and reconstructing them with additive synthesis techniques, delivering expressive, organic performance that stood apart from static samples. The MKS-20 has been heard on countless ’80s recordings, used by Elton John and Thomas Dolby and is still favored by professionals. 

The unit is actually in excellent shape but I listed it as "Very Good" as the read-out screen has dimmed over the years. (Excellent hack: If you shine a flashlight on the screen it becomes easily readable from a few feet away.) All the sounds, FX's knobs and buttons work excellent and the sounds are clean.