As Guy notes, it is certainly a plug board but it looks to me like one of the smaller ones that were found in machines such as sorters, reproducing punches, and collating machines. The boards in the accounting machines such as the 401 were, as I dimly recall, 3 feet by 2 feet. In fact, almost every machine had a plug board of some sort. They were in use (at least in computing backwaters) until the late 60’s. As with the graphics on the tops of decks of cards, there was a colorful artistry in running the wires in a plug board as each length of wire was of a different color. There was no need for short runs so long wires could be used even when short wires might suffice. The true wiring virtuoso could plug the board so that you could actually see how the computation was being performed simply by contemplating the wires. As a side note, sorters had a second life in carnivals as ``handwriting analysis machines.’’ One wrote something on a tab card and handed it to the person in the stand. Your card was combined with a stack of cards and placed in the sorter’s hopper. With great fanfare and many blinking lights, the sorter was activated, the cards flew into the slots, and you were handed the cards in the first slot as the analysis of your handwriting. But I digress. Cheers, Scott