colorado hirailer posted:Idle off-topic question about Chicago Flyer vs. ACG . Did only ACG, and not CF, offer O gauge three rail "scale" trains as those known for zinc leprosy just prior to WWII?
All manufacturers of trains pre-WWII made items that could be prone to "zinc pest". Zinc pest is the result of lead containation of the zinc alloys used for die casting. Over time the lead precipitates out of the alloy solid state solution resulting in dimensional change, swelling, and internal stresses which crack the part. Dorfan is the most prone; however Lionel, American Flyer Manufacturing Co., and Gilbert American Flyer may be subject to the problem, sample to sample. AFMCo. trains were made for the most part of sheet metal and cast iron, but add-on pieces such light housings and wheels can be affected. Pre-war Gilbert 3/16" scale is more prone to the problem because more die casting was used in what was a new (for the time) line of steam engines and die cast rolling stock. The worst examples are with the prewar Gilbert 0-8-0 switchers from 1941. Lionel scale Hudsons, the chasis of 390E's and 400E's, and cabs of 265E's (as examples) may be afflicted, as well. Luck concerning lead contamination, or rather the lack thereof, determines whether a given piece is affected. During the course of WWII, the origin of zinc pest was determined out of necessity and the problem for the most part was eliminated. The problem does occassionally show up in modern fabrication if the factory was not diligent.
The good news is that the lead precipitation is a time dependent process with specific kinetics. If it has not shown up by now in a vintage train model, it is not likely to occurr in the future. So, a careful examination of a vintage toy train is the key to avoid buying one with the problem in a potential purchase. In many (but not all!) instances, replacement parts are available for repairs.
Maybe more than you wanted to know, but there you are. 
Bob
