For German trains there's a 1950 Liebmann catalog at ddr-spielzeugmuseum-aschersleben.de. It can be hard to see; click on the small images you can see the model numbers and read the text.
Three Zeuke catalogs from the 50's are at calameo.download.
train35.fr has a few catalogs from the 50's, including a 1959 JEP catalog that I think is not on any of these other sites.
Otimo