Try posting your question on the Mini Mania discussion board
https://www.minimania.com/msgthreads.cfm There are people on there from all over. Even if the owner of the car isn't there, somebody else may know who's car it is.
Regarding the age: UK cars discontinued the external hinges in 69, but in Australia they continued much longer. The Australian cars had wind-up windows and external hinges. Because of the mild climate in parts of Australia and New Zealand, a lot of cars have remained very rust-free making them very desirable for import. The favorable exchange rate helps too. A lot of Australian and New Zealand cars have been coming into the states recently. There are a few other age clues that are less conspicuous (tail lights, grille and a few others) but it's not uncommon for people to retrofit older styles, or update to newer. A large part of the Mini culture is customization.
As far as the waving, I doubt the Mini driver took offense. You quickly get used to being waved at when driving a Mini. It happens several times every time you take the car for a drive.
[ 11-10-2002: Message edited by: zanzibar ]
[ 11-10-2002: Message edited by: zanzibar ]</p>