The frame is made of steel with really nice lugs and good quality brazing and very good paint. There is no rust anywhere. The mudguards are probably stainless steel. Again, there's no rust. Other parts are aluminium, and of course there's a bit of plastic and rubber.
I can still buy all the inexpensive parts I need to repair this bike, but I can't get the parts required to repair some modern bikes. Electric bicycles in particular become completely unmaintainable after a few years so I usually can't help people with those. But if you have one of these lovely old bikes and you take a bit of care of it, it'll last your whole life.
This is the level of reliability we should demand from manufacturers of everything that we buy.