Hi,
On the subject of unusual plugs, here's an early offering from MK. I think it dates from the early 30s. It's a 15amp 2pin plug with a 5amp 2pin socket in the top. The socket is supplied via two wire fuses.
To wire the plug, the cover is removed and the ceramic interior is then pulled off the thin pins. The black bakelite cover is painted brown.
Cheers, Pete