This is a diode 'plug in' module from a Burroughs B5000 mainframe. The Burroughs B5000, released in 1961, was a large commercial mainframe which contained many revolutionary features for the time, including multi-processing capability, instructions for handling strings, memory protection, and high modularity. The B5000's logic systems were built up of large square plug in modules, which contained a number of transistor and diode cards such as these. These plug cards are in good used condition, as shown in the image. Give yourself a legitimate reason to say "I Touched a B5000!"