Great flea market find! Casiotone MT-600 in fully working order, including MIDI control. Here I demonstrate the basics of using such a device with a modern Novation Launchkey, as well as interfacing with Ableton Live.
Note that according to the documentation, the Casiotone only offers internal control of it's own drum machine. I have a feeling with more tweaking, I could get around that, but I wanted to get this posted with what I have.
Also, the Casiotone uses MIDI CH 4 for drums, which is unusual since the "standard" is typically MIDI CH 10. Again, more exploration is needed to exploit the drums over MIDI. I was mainly interested in the many keyboard sounds.