Tom Hood (who started C-D-S) had an extensive collection of freight car slides. Years and years ago Ken Goslett introduced me and my friend Arnt Gerritsen to Tom and we spent an enjoyable day in his basement as he loaded box after box of freight car slides into his stack loader.
His lettering sets were based on that collection and you can bet that if you have a diagram of a GACX/Rexall Chemical airslide, Tom had a slide of THAT CAR in his collection. We provided Tom with the photos and data to produce Ann Arbor RR freight car sets and we had to lobby hard to get him to include an extra number jumble in the C-D-S sets to allow us to do more than one model. His early sets had only the particular car number that appeared in his photo.
