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.