[Joe F]

Found this "receptacle" in my father-in-laws house. Mid-Atlantic brick colonial built in 1943. Wires inside are disconnected (and probably have been for a long time). Appears to be low voltage wire. I have no idea what it is.

 

[circuitman]

it's a plug for an antenna for the old radios, saw them posted on electrican talk.some have the 120 plug below.:smile:

 

[Oso954]

Here's a pic of the "duplex receptacle" of the type circuitman referred to.
The aerial/ground jack above, power receptacle below. The aerial/ground plug is shown to the left.