This is two years late, but the terminal the original poster describes sounds like an IST (model 1), a CRT-based CDC product, vintage about 1978. There was a later edition called the IST-II, also CDC. It had two 8" drives and a Z-80 CPU, as well as connectivity to CDC PLATO mainframe systems, either by dialup modem (1200 bps) or multiplexer. The IST is not the oldest PLATO terminal, but it is the oldest that CDC manufactured, I suspect. Even my PLATO IV (Magnavox, 1971) is not the oldest, but only the first mass-produced machine. The earliest ones date to about 1961 and there are probably only two or three still in existence, if we're lucky enough to have that many. A precursor to these would be Norman Crowder's Auto-Tutor, vintage about 1958, which has characteristics very similar to the PLATO terminals (though it is not a computer terminal, it operates on filmstrip media), and PLATO's mechanisms are said to have been influenced by this machine. Peter Zelchenko (pete(a)suba.com) Chicago, Illinois