Don't really mean to bring this topic back up but while I was doing electrical work to my own house,, (actually my apprentice/helper) ran into the same plug in my office. The neet thing about this is that most of the wiring is still intact. On the top part of the receptacle, their was old RHW # 10 AWG attached to the Aerial side, up the wall to the attic where it was then attached to one side of an old lightning arrester (the top side) parallel (looped) to the same wire to one of the attic windows where it was just hanging their with a metal strap soldered to the end of it.
On the other terminal marked ground their was # 10 rhw running up the same wall to the attic to the bottom attachment of the lightning arrester then parallel (looped)down to the Stink Pipe Chase where it just hung to the point of my Basement 2 floors below.
Now this is where it get real iteresting.Their was an old Knob and Tube circuit that fed its own duplex receptacle about a foot away from the (radio receptacle) so their was no need to run power to the bottom half. Their was however three # 18 AWG RHW se prate conductors terminated with tape in the same device box that this (radio receptacle) was in. I also have to add that in the same room their was a met el duplex brass plate with a finished hole drilled through it that was on another receptacle. I am only guessing that over the years the plates got moved around for painting and that the plate in question was for the Radio Receptacle. I don't know where the other side of the # 18's go to as I hate doing electric work in my own house but if I was a betting man I would have to guess it was for a remote key and speaker. If that was the case then this must of been a real nicely wired house for the time. Anyway I will try to include pictures if I ever figure out how to use my camera
