OK, had to register, I love that outlet! But it simply does not make sense that DC loads of the day would need polarity reversed, unless there is an item I can't think of at the moment. I collect antique radios, and radios that plugged into the mains outlets did not come on the scene till the late 20's, and AC/DC radios did not come around till the early 30's. Universal motors, lights, heaters, don't care about DC either. Were AC plugs polarized by 1922?