It's probably an E-3, which was created as part of a free-trade deal between Australia and the US.
https://en.wikipedia.org/wiki/E-3_visa
Source: I've had one.
https://en.wikipedia.org/wiki/E-3_visa
Source: I've had one.
Also, I don't know why you guys would be giving us thank you privileges for ww2. We were at a lot more risk from Japan and you put in far more work to stop them. If anything it'd be the other way around!
As for the thank you, it was probably compensation for whatever damage was caused to the MCG. ;)
Either way, us Australians are certainly lucky to have this visa.