War story: In the photo of the two receptacles in corroded 'bell' boxes, the right locking receptacle was used almost universally on construction sites (up to early seventies.) At that time usually two were mounted side-by-side on a temporary power pole, with one labeled '110V' and one '220V.' (Honest) The manufacturers' rating was 20-amp 125/250-volt 3-pole 3-wire. (I think one type was a Hubbell 7310.) The keyed blade was used for the equipment ground, even though its associated screw head was NOT green and NOT a hex head. It was common to lay out TWO cords--12/3 SO side-by-side, and each crew had their own wye adapter to feed their tools. And yes, there were incidents of plugging into the wrong cord. At least most power-tool housings were grounded. :-) Stranger yet, in many plants there were locking three- and four-blade wiring devices that had ratings like “20A 250V / 15A 600V.” :-( So much for ”the good ol’ days.”
