I believe I installed a couple of these in the early 80's.
MDI control means to go to a point and store it, on to the next point, etc to make a program. Cannot tell you more than that. Hardware is generic Bridgeport. Motors are SEM thus still serviced. Control is obsolete. Not ever considered a true CNC thus the limited sales.
Probably low hours (for a reason) thus good hardware/platform for a retrofit.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)