Welcome to this website - lots of Opel info here.
Though 649,512 Kadett A's were made from 1962-65 most of them died of rust.
Never seen one here in New Zealand because the Vauxhall Viva HA was sold here instead as they were the equivalent GM car for this region - probably the same in Australia. How long since you saw an HA Viva?
The only early Kadett I have seen in NZ is my 1967 Kadett Rallye "B"
http://www.opelgt.com/photos/showphoto.php/photo/7214