Found this one during the holidays, there was a whole row of these in a parking lot at the insurance company. about five, and a few have 2 romex cables, and like one or two had extension cord/romex in one plug, and was wired into the parking lot lights with a surface mounted transformer to bring the pole light voltage down to 120V. i still wonder how the insides of those cord caps looked
I have been involved with Safety and EMI test labs getting product tested for compliance regulations. They usually full of "interesting" wiring practices. 240V 50 Hz bus ducts with 15 & 20 A US recepticles, 240V in 0-280V out Variacs with oversized fuses and electrical tape for fuse covers. 10 KW power supplies with multiple energized output leads just clamped to a piece of wood. Most of the power cord whips I saw had the just the insulated conductors hanging out of the back of the plug. Occasionally I saw the cable just poked thru the knock out with no attempt of strain relief.
The how doesn't look that hard. Those receptacles use the washer/screw termination. I imagine they just stabbed one wire down each side and tightened the screw. (like a QO breaker) I bet the handy man was proud of himself and thought it was an elegant solution.