Need PDP boards identified

I need some help identifing some of the boards that I pulled out of Paxtons yesterday: M7904 - Not listed in the Field Guide Hex-Height 40-pin ribbon cable sticking out the side NDLV-11 netcom products, inc. copyright jan. 1979 MSI-11 (c)1978 Andromeda Systems Inc faded sticker on handle says 'MUX1' and 'MUX3' the rest is to faded to read A two board set from Plessey Peripheral Systems connected via a 50-pin ribbon cable. The top board (P/N 703580) has 8 LEDs and a 10-pin connector. The bottom board (P/N 703570) has 4 26-pin connectors and a roughly 66-pin connector (not sure its exact size). The only thing I can think of is some kind of drive controller. Zane | Zane H. Healy | UNIX Systems Adminstrator | | healyzh(a)aracnet.com (primary) | Linux Enthusiast | | healyzh(a)holonet.net (alternate) | Classic Computer Collector | +----------------------------------+----------------------------+ | Empire of the Petal Throne and Traveller Role Playing, | | and Zane's Computer Museum. | | http://www.dragonfire.net/~healyzh/ |