jag2 All I can tell you is the "sender" is a reasonably large seller that sends out a couple of hundred guns a month (admittedly not all are C&R) and they are always in one of those special one price USPS boxes. Its not like he could fly under the radar so I'm guessing his local post office knows whats going on.
Typically USPS/UPS/FedEx clerks do not know every law, regulation or tariff that is on the books.
Neither do gun dealers.
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Plano, Texas...........the Gun Nut Capitol of Gun Culture, USA https://www.youtube.com/watch?v=pELwCqz2JfE