The fischer cars were all scratchbuilt/custom built. They were built of layered strathmore board. As I understand it, he sealed all the sides and parts with shellac or varnish so they would not warp. but if one gets rough usage, I would think moistrue could get in and cause things to happen.
I have seen some very nice ones and some rough looking ones. My opinion is, I would not buy one from photos on the net. I would want to look at it in person.