1987 Yamaha Japan SHS-10S Keytar ("Gui-Board") w/MIDI
The Yamaha SHS-10 (or the Yamaha Sholky if you're in Japan) is a Japanese made keytar that was released in 1987.
Compact keyboard with 32 minikeys and a pitch-bend wheel, vibrato and sustain buttons, an internal Frequency modulation (usually referred to as FM) synthesizer offering 25 different voices with 6-note polyphony, two operators, and a very basic chord sequencer. It also has a loudspeaker for use on it's own (or plug into an amp through a Boss FZ-2 and use Trumpet mode for some genuinely dangerous sounds).
Tested on power supply (not included) and is working perfectly, good overall condition, missing battery door.