I’ll wait for it to come around on the guitar.
I’m very doubtful about this story. The only reference I can find to this acronym is an unsourced entry on acronymfinder.com (which notes it as being in use c. 1900, btw, not c. 1943).
Also, there is no such thing as the U.S. Department of Engineering, and I can’t find any evidence that an entity by that name has ever existed. The Army engineering branch, which managed the Manhattan Project, was at the time (and still is) called the U.S. Army Corps of Engineers.
The nomenclature doesn’t even make sense. The term “Department” in the U.S. Federal government is pretty much always used for executive branch agencies with a cabinet secretary, and the U.S. has never had a “Secretary of Engineering.” And the official name takes the form of “U.S. Department of X”; the form, “X Department”, is usually only used informally, not stamped on Department property.
Addendum to the above:
It’s possible that some incident like that occurred involving the U.S. Department of Energy, but that agency didn’t exist until 1977, and I personally find it unlikely they would stamp their property with USED (U.S. Energy Department) instead of USDOE (U.S. Department of Energy).
I kind of puzzled about it myself. I was wondering if it was some sort of subset of the Army Corps of Engineers who were the ones in charge of the project.
Actually what makes it illegal is a law passed in 1934, not what is stamped on a mailbox.
Never let the facts get in the way of a good story 