I don't know what's wrong with the australian site given in IMCDb links, but it doesn't work on my computer. No problema, I was just given a new one:
http://vre.vicroads.vic.gov.au/
Just check the "I understand..." and click on "Continue". The search can be done on the registration number, the VIN (Vehicle identification number) or the chassis number.

I also found some times ago a site for the new French plate system: it's not an official one, just a site based upon official statistics and data, and aimed to give the date of arrival of a number you'd like to have on your vehicle: for example, if you want your car to have the MB-300-SL registration number, you'll have to wait until 05/03/2031
But it can also give you the date of (new system) plates already allocated.

/!\ The new system (SIV) gives French cars a life-long registration number since April 2009. So knowing the date of the plate allows more or less to know the "date of birth" of the car (which could have stayed some months at the dealer's store before being registered). But pre-2009 cars will also be given an SIV number.
So keep in mind this tools is really trustworthy only for vehicles unveiled for sure after mid-2009.

Thanks, I'll update the links on the site

For Australia, the site in the links is for New South Wales and your new link seems to be for Victoria. So they are complementary.
Or does the new site work for plates of all Australian states?

The truck for which I was given the link is indeed from Victoria and the domain name is vic.gov.au. I should have noticed it, but I think I'm too used to "whole country" tools
Australian states are that huge it's impossible to have a general site for this? I understand why it's called the "island-continent".

I guess it works in a way similar to US states.
Being from Belgium, it does not seem strange to me to see things managed at a smaller level in a country, as here we are probably the best for having useless power levels and multiple country divisions (regional, linguistic, provincial, community)

@antp - please add Queensland (QLD) to the list of links for plate information:

https://www.service.transport.qld.gov.au/checkrego

Thanks.

done

@antp - another link for plate ID. Northern Territory (Australia):

http://www.transport.nt.gov.au/mvr/rego-check

Although the chances of someone having to use this link are slim

done