When the diecast zinc parts begin to crumble apart.......the bodies, the chassis, the wheels, everything made from diecast zinc........
I heard this from a guy who has to much post-war stuff. (like you can 
) He once told me that the main reason for zink pest is because the people who melted the metal would through there used cigarets into the melting pot. This would then cause deformities in the metal and when the air tried to get out of the metal, the end result was zinc pest. Now I don't think that would be the case for the cause of zinc pest in the modern stuff but who knows. Also, not too long ago I purchased the 6-18005 "700e" and I can vouch that it is a very nice engine. Runs smooth as silk and looks elegant standing still or running.
I’d think it more likely that the metal was simply not of sufficiently consistent quality.
https://en.m.wikipedia.org/wiki/Zinc_pest
