I strongly agree. When I take notes and put files in geographic directories, I still use .oz.
How was it used?
I'm guessing that's Australia.
Correct. Fun fact: For many years after the rest of Melbourne University moved to unimelb.edu.au the computer science department kept the domain cs.mu.oz as a nod to that history (and that they were one of the first institutions in the world to be part of the fledgling internet). I was a little sad to see that quirky disappear.