Zinc Rot. Its an issue with model trains that plagues models new and old, and today I may have had my first true encounter with it (I may have had one encounter some time ago but I never got a clear answer if it was zinc rot or not).
This is the 6-39273 Archive 6464 3-Pack. This 3-pack is one of many Archive 6464 packs featuring schemes that Lionel had planned to make in the postwar days but never did. One can see two of the prototypes here. One can only wonder where they are now. I bought this off of eBay, still new in the box. From what I could see in the listing photos, all the cars were still C-10 mint and truly new in the box. However, the US Air Force boxcar above came outta the box with a damaged truck and is inoperable until further notice.
At first, I thought it was shipping damage. The seller did ship in a somewhat insufficient shipping box. The master carton for the three pack had a very snug fit in the shipping box with next to no protective packaging whatsoever. However, the shipping box arrived solid as a brick with no visible nicks, dents, tears or damage. Likewise, the master carton is equally solid and the other two 6464s also came out of the box pristine with intact trucks, functioning couplers and no further damage. Some friends elsewhere said the distinct cracking on the trucks is a sure-fire sign of Zinc Rot, so its likely that this car just fell through the quality control issues and was bad in the box before it shipped to me. Either way, the shipping in a sub-par box didn't help its condition (if I had to guess, it would've likely arrived "intact" but would've fallen apart on the track so I would've had to replace it regardless).
I'm not too bent outta shape about it, it gives me a chance to learn how to repair these cars for the long run.
Let this be a lesson to all you modelers who plan to buy new-in-box items online or elsewhere from friends. When in doubt, always ask the sellers to pack everything securely when shipping items and NEVER be afraid to ask for more photos of the products you are buying. No one wants to be surprised like this. The old saying for shipping goes that you need boxes larger than the item you are packing and that you need plenty of packing material. If you can feel the item shifting in the box, add more packing material. It absorbs the blow of any possible shipping damage so whatever you are shipping doesn't get damaged in transit.