The plastic on vintage computers gets brittle with age. I asked the seller of this TRS-80 Model I Expansion Interface to remove the power supplies from the expansion interface and pack them separately in the box because through past experience, I knew the plastic case wasn't strong enough to handle the stress of two 3 lbs objects during shipping. Instead, the seller just tossed some packing peanuts in the case and screwed the lid back on thinking it would work. It didn't.
There was no obvious external damage to the packing box, and in fact, the expansion interface was otherwise well packed. This was an eBay item, and the seller offered a refund.
(click on picture for a full size version)