yaktx,
Regarding the crows foot outlet, there's no continuity to the mounting yoke from the vertical pole, The way the outlet was wired was a little different, and I'm not sure if it was acceptable at the time or not... The T-slot outlet was wired typical, but the crowfoot outlet was wired 240V between the angled blades and the neutral from the T-slot looped up and over to the vertical blade of the crowfoot... I took it out and replaced it with a Nema 5-20 duplex and split it for 2 dedicated ckts.

The outlet in the first pic is from a house built in 1900 in Compton, CA.. It's the only duplex of it's style I've ever seen (So of course I had to recommend it be replaced [Linked Image] )There isn't any polarity to it, although it's worn to the point that a polarized plug will insert into it. I have a few of the single style ones from the same house and a couple others built in 1898 and 1903 (I got some snazzy pushbutton switches from those houses also [Linked Image] )
Just for the sake of it, I tweaked an old 2 prong plug with a pair of needle nose a little bit and it fit into the crowfoot plug just as if it was made for it, showing the blade spacing is close, if not exactly the same.

It is interesting to think of having grounded outlets waaaaay back in the day, but compared with our modern NEMA 5-15, 5-20, etc... there is one thing of signifigance, and thats the fact of the ground pin being longer than the current carrying blades... Ensuring that the plug has grounding contact made before making energized contact.. (Now if we could make some foolproof way of keeping 5-15's from being installed without a ground wire [Linked Image] )
Yeah, we still have millions of homes lit with knob and tube, and other ungrounded systems.. "More work for us..." Job security [Linked Image] [Linked Image]

Randy

PS... the outlet on the top didhave 50 coats of paint on it... 2 words, "Goof Off" [Linked Image]