Looking at the Wikipedia pages here, I find it amazing that computer design had moved so quickly between 1953/4 when the Ferranti Pegasus http://en.wikipedia.org/wiki/Ferranti_Pegasus And IBM 704 http://en.wikipedia.org/wiki/IBM_704 were produced to the PDP-1. http://en.wikipedia.org/wiki/PDP-1 looking at the PDP-1 card here http://en.wikipedia.org/wiki/PDP-1#mediaviewer/File:Dec_SYSTEM_BUILDING_BLOC KS_1103.jpg I notice it uses the same PCB connector as my EAI-TR10 Analogue computer. Now whilst I can find the sockets, I can't find any of the PCB mounting plugs, and I "need" one to make an extender card. I can make one up from PCB but it would be nice to have a real plug if any one has one they would be willing to part with. Dave G4UGM