Originally Posted by wa2ise
That picture would make a good addition to the Wiki article on obsolete power outlets,
http://en.wikipedia.org/wiki/Unusual_and_obsolete_plugs_and_sockets
I could upload it to there if okay by you.

At last the answer to the question I've wanted to know for a long time; as I've suspected all along, the Australasian three pin plug has the same pin spacing as the 'obsolete' US counterpart on which the design of it is based.