KORG Vintage Poly Ensemble P Keyboard K-4

via this auction

"Often also named Poly Ensemble or K-4 was build from 1976 to 1979/80 it is often mistaken as being little brother version of the Korg PE-2000. But this is not like this! The parameters available, the technic inside and of cause the sound are very different. Its main feature compared to nowadays keyboards is its full polyphonic structure. That is, each and every key will make a sound at the same time (if needed). No voice stealing on long release time notes. It is build like so many keyboards of this time in a suitcase like box with a detachable lid."