Tektronix Microlab I

Well Tektronix stuff is still finding it's way to me! I went out this morning and found a Tektronix 7D15 Counter Timer plug-in and a Tektronix Microlab I in the bottom on a basket of scrap. Does anyone know anything about the Microlab? I thought it was some kind of digital trainer but found a referenece on the net, <http://www.spies.com/~dd/TE/Tillman/Tek7000-Tillman.html>, about it being used with a special interface board to test Tek 7854 o'scopes (presumably the digital sections). It's mounted in a blue case similar to those used for the Tek 83x Communications Analyzers. Once you open the cover there is a hinged clear plastic cover on the LH side inside. The clear cover has a square opening that leads to a card slot in the main unit. On the RH side is a panel with an 8 digit LED display. The left four digits are labeled "address" and the right four are labeled "data". Below that is a hex kexpad. There are also four more keys along the RH edge. They are labeled "reset", "load address", "load data", "inc" and "dec". The sixteen hex keys also have shifted functions that look like something that would be found on a digital trainer. One the left side of the case near the rear are two 1/8" jacks that are labeled "cassette in" and "cassette out". One the right side of the case near the back are two DB-25 connectors, one labeled "RS-232 terminal" and the other labeled "RS-232 MODEM". I opened the case to check inside and found that it only has sone circuit board in it. It has a lot of TTL ICs, some 2114 RAMs, three 6850 UARTs but no CPU! I suppose the CPU is on the plug-in card (that I don't have :-( Anybody know anything about these? I couldn't find anything in my '86 Tektronix catalog and only one mention on the net. Joe