Hi Jack.
There's not really anything too strange about this receptacle. It's made (or was made) by General Electric in the late 50s/early 60's, it's obviously only a two-wire model (with both slots being the same size, which prevents use of newer plugs with a slightly larger neutral), and you could connect four items at the same time, if the plugs were all a flat type.
I have a couple of these in my collection, just more as an oddity than anything else.
Mike (mamills)
