Here's a Flyer 633 B&O boxcar in rather poor condition, but once a valued part of the collection:
File comment: AF 633 boxcar
Flyer 633.jpg [ 147.94 KiB | Viewed 4667 times ]
It's old and dirty, hasn't seen the light of day in many years, but it's value was that a previous owner had taken a 600-series link-coupler car and converted one end to a knuckle-coupler. The point of doing this was to make it possible to assemble a train that consisted of both link and knuckle-coupler cars. It saw a lot of use back in the day.
As can be clearly seen in the photo, the car suffers the fate of many early postwar Flyer rolling stock in that the bakelite shell has distorted over time, producing an unsightly hump in the roof-line. Bakelite, an early plastic, doesn't hold up too well, at least when American Flyer used it in making their postwar trains. It was used for many other things as well - electrical junction boxes, jewelry, casings on appliances, automobile parts. One occasionally sees the warpage in those as well (but not as often as I see it in Flyer trains).
Everyone frets over zinc-pest, the rot that afflicts some metal diecasting, perhaps because that typically manifests itself in the pricier toy locomotives. Interestingly, everyone knows what causes that, yet it still happens today (primarily due to carelessness, or even shortcuts taken, in the manufacturing process).
But I've not seen anyone despair over the warpage of bakelite in Flyer trains. Perhaps that's because there are so many fewer S-gauge fans.