I was in a 1976 house and found this wall plate/receptacle. The buyer was in my back pocket the whole time I was there and distracted me and I forgot to go back and pull the plate to see how it was wired or what was connected to it.
Not sure how it’s wired, but a brief description here.
http://www.fam-oud.nl/~plugsocket/NorthAm2.html
“4-plug socket, rated at 15A-125V. The socket is polarized. Right and left slots are respectively 8.44 and 7.24 mm wide.
Brand name: General Electric (wiring device department, Providence). Socket design probably dates back to mid 1950s.”
-Carl
Good call Carl. 
Definitely a GE product, saying that as a past
GESCO purchasing agent.
Thank you Carl.
You’re welcome. It’s a nice site for those old-timey outlets! 
-Carl