So I finally figured out what it was
 

I had noticed that the apartments in a building I do work for had an electrical outlet that didn't work. They had long been painted over and ignored. I figured they were old non-polarized plugs and left there when updated in the 50s to newer and more outlets in each place.

A while back I decided to free one from its tomb and it was a single outlet with two wires connected to it. I put a plate over the box and took it home. When I got home I started to clean it up and it turns out that it's not an outlet for power, but an outlet for radio antenna. Seems one side is ground and the other goes up into the attic of the building where there's a long copper wire run the length of the building.

I looked all over the internet for these things and can't find anything of use. I gave it to my brother as it seems his house also has the wire in the attic, but his outlet was removed years ago. He now has his old Philco hooked up the proper way.

There were various styles of radio and TV antenna outlets made over the years. I've seen a radio outlet from the late 20's that was a single power outlet with two 20's speaker connector style jacks on it for antenna connection.

I think I have a plug for this type of outlet.

It looks like a small bakelite lamp plug but one prong is turned 45, the other 90 degrees making it highly unlikely to insert in a standard power receptacle.

The brass prong is stamped "aerial" and the other is silver "ground". Manufacturer is also stamped on the brass prong: Arrow Hart and Hegemann (AH&H)

That's the thing. This one looks just like an outlet (one before the wider neutral). For more than 20 years I thought they were disconnected outlets. If I hadn't of cleaned it and read "ground" and "aerial" on the face, I would have gone on thinking they were electrical. They're an ivory bakelite.

I'll take a picture of it when I'm at my brothers on Tuesday.

At the house where I got my 6-T-84 combo, my CTC-17, and my G>E> portable these outlets were in every room. I also got a box of the leads that connect to the set and plug into these outlets.