An interesting article on the E26, E27 sockets. I'd be surprised if anyone knew what they were using.
Another story about sockets. We replaced our caravan a year or so back and when plugging in a cigarette lighter type plug for 12 volts to charge a phone or what ever, it would blow the 12 volt fuse. Odd. It appeared, when I dug deeper, that the stupid Brits had taken a bit of metal from the centre pin up the side of the socket so it shorted to the side pins. Why? Absolutely no ideas why any designer would do something as stupid as that.
I replaced all 12 volt sockets with NZ available ones.