The goal, postal inspectors said, is to get people to remember where the mail came from.
Officials said anyone who had received such a package should contact a postal inspector.
In September 1991 postal inspectors looked over their mail room.
But postal inspectors liked to be known as the 'silent service' back then.
He submitted his proposal in 1944 while working as a postal inspector.
They notified company security officers, who called the police and postal inspectors.
Federal investigators and postal inspectors have played down the significance of this letter.
No one will look for such mail until then, she said, because "postal inspectors are not going to be put in harm's way."
A postal inspector has spent the last five or six years trying to track one down on his own time for posterity.
According to American, the postal inspector said he had never filled out such paperwork in the past, despite having traveled with a gun.