I have to ask, is the earth contact a single piece with spring tension, or is it two pieces, like two "L"'s that are held in place by a stud under that nice termination lug?
Or, is your earth pin much wider than the other pins on the male cap?
John,
One side of the contact is brass, the other side is copper.
Usually there is quite a bit of "spring tension" between the two contacts, that holds the pin of the plug in place.
As far as I'm aware, the pins are all the same size, it's just that the earth is longer.