I agree, there is an old town near me where I have seen these used extensively, because many of the houses were built pre-electricity, so they had a lot of surface mount wiring and devices used, especially where they had used old gas piping for running wires into light fixtures. Since the entire box was Bakelite it was non-conductive, so no ground wires back then and no real risk of that neutral yoke contacting anyone once the cover was on. First time I saw one I was confused too, but my old J-man who had started working in the 40s explained them to me.