I thought the UL1 would be a clue but I have now seen pictures of Augat UL1 boards without an edge connector!
I must admit at the time it was quite common to have prototype boards that although having an edge connector did not meet any particular bus standard as the mating connectors (for the backplane) were widely available in different numbers of ways and pitches. This one seems to have 60 ways, one or two sided ? and pitch ?
I myself built loads of stuff on these with all sorts of proprietary interconnects, remember in those days most backplanes including computers were wirewrapped so anything goes! and not necessarily bused to all slots but function dependent connections, sometimes a processor or graphics, memory function would be chopped up across many slots even using large 15" square pcb's (that were quite common).