I sent this bike frame to someone who'd been looking for one to build up last week.
Here are some before and after pics. I know it wasn't an expensive bike but it had no rust at all, had survived 24 years without any damage and would have done another 24 with no trouble.
It was well packaged in a bike box from my local LBS.
Looks to me as if it was run over by the delivery van or fork-lift truck.
Discussions still ongoing with the carrier.