I have a box of those Twist loc rec. It is a non grounding type. They were common used during the late 1950 & 60's on fire apparatus. Used on fans & lights. They made a 2 conductor also. They were frequently miss wired as the screws on the early models were not identified. I was in a fire dept that used these. Several of the lights were mis-wired. When you started the generator on the pumper and stretched the cord to a light set on the (wet) ground, if you touched the truck, you got a tingle. One pole was grounded in the generator and the other on the light. Replaced them all with grounded and properly wired TL.
