These cars are a fascinating case study in Lionel's production techniques, as numerous running changes were made in the cars during their production. The MPC/Lionel team was learning as they went along in the early '70s, and design changes were made in the cars' bodies, trucks, door guides, and packaging. No other group of cars in the MPC era can approach the 9200s in the number of subtle but interesting variations.
I used to look for the early MPC cars, including 9200 series, that came with modified Timken trucks. They had fast angle wheels and plastic "thumbtack" couplers. They didn't actually have thumbtacks, a small rectangular metal bar was glued to the bottom of the armature. They often fell off.
The trucks had a very grainy appearance. A while back someone wrote about the cause, but I don't recall what it was.
