NICE! The bottom 2 pictures look like they are made of solid brass. The first picture looks similar to the one I posted here several years ago.

It is, Your post got me looking for one. I had a search on Ebay for two years, never found one. Then a guy saw my display of other old outlets at a antique engine show and asked if I had ever seen one. I told I had and was looking for one. He sent me a outlet only for the postage. Nice guy!) Two weeks later the one shown above showed up on ebay mislabeled. no one else bid on it.

I have since found a competitor the only marking is a "S" tipped about 45 deg on one blade of the ant plug.

I found yet another. This time a box of 5!
http://lbpinc.com/Aerial-Ground-Power.jpg

I just came across some of these in a 1930 house that are antenna/ground only, no power. Two of them are in the center of the rooms in the floor with no power nearby. I can't imagine why they put them there with no power. They are just a single, round receptacle just like the top half of the ones shown. I have pics but don't know how to upload them without using a host site and I no longer trust photobucket.

OK here goes. This one is right out in the middle of a concrete floor in the dining room

Could have been for a crystal radio or a battery operated set!

It says a great deal about the durability of its construction.