In article ,
sponix writes:
Some old electrical fittings he

http://www.74simon.co.uk/plugs.html

Very interesting page.
Some of the dates are wrong though -- 13A plug was introduced
in 1946, and BS546 round pin plugs go back well before WWII.
Also, there were 4, not 2 ratings of BS546 plugs; 2A, 5A, 15A,
30A (which you would not find in the home, but was used in
industry).

--
Andrew Gabriel