Dunno. One of mine is rusty in the boot, but that's only where I welded it together since I got it as an insurance write off. One I had for a bit had a couple of holes in a sill. But that's it.
I first discovered they were galvanised when mine got a bit of paint chipped off. I never got round to putting some back onto it, and I was pleasantly surprised when it never started rusting. Mine have all been the later ones though.
(I remember discussing this a couple of years ago and finding a picture which showed which bits had been galvanised - eg the roof wasn't. But I can't find it now).
Fortunately the BX fits that bill.
We may be talking a different sort here - however my good ones all carry two people...
cheers, clive