"incompletely blacked out barcodes from the previously used box"

Bingo!! Although not quite as involved and certainly not as valuable, I had a similar incident occur and the explanation was exactly the same!! Although it is easy to criticize and get angry, when it comes down to the Optical readers/bar code readers, etc that everyone now uses in the semi-automated shipping process it does at least make these things a bit easier to understand. For that very reason, I now ensure beyond a shadow of doubt that if I use an pre-used box the old codes, etc. are completely obliterated.

Perry M. Kissam
NRA Patron Life Member