Discussion about the Korg PolySix synthesizer

Hi all,
New to the group here...I hope someone can help point me in the right direction.

I recently picked up a cheap/ used PolySix and noticed that it had been MIDI retrofitted. There's only one MIDI female plug on the unit, so I'm (albeit naively) assuming that it only has a MIDI-IN function. I don't have a manual for this particular retrofit, nor is there any indication really of which company supplied/ serviced it...or when for that matter. I see there are about a million of these retrofit kits available on the web. I'd really like to be able to use the MIDI-IN function just to control notes and sequences, any suggestions on where to find the correct manual etc?

Many thanks in advance!
Jake