Silent Service (United States Postal Inspection Service or USPIS nickname)

The United States Postal Inspection Service (USPIS) remains little-known, even though it claims an origin back to 1772 and colonial Postmaster General Benjamin Franklin. The USPIS investigates all crimes that use the U.S. mail.
 
The USPIS nickname of the “Silent Service” (cited in print since at least 1973) reflects its relative anonymity. Unlike the formal name of the Secret Service, the Silent Service is an unofficial nickname. Submarines during World War II were also called the “Silent Service,” and this might have preceded the USPIS nickname.
 
   
Wikipedia: United States Postal Inspection Service
The United States Postal Inspection Service (or USPIS) is the law enforcement arm of the United States Postal Service. Its jurisdiction is defined as “crimes that may adversely affect or fraudulently use the U.S. Mail, the postal system or postal employees.”
 
An agency with approximately 4,000 employees, 1,200 criminal investigators, an armed uniformed division with 1,000 personnel, forensic laboratories and a communications system, and with 1,000 technical and administrative support personnel, the USPIS leads and assists in numerous joint federal and state investigations.
 
History
The Postal Inspection Service has the oldest origins of any federal law enforcement agency in the United States. It traces its roots back to 1772, when colonial Postmaster General Benjamin Franklin first appointed a “surveyor” to regulate and audit the mails. Thus, the Service’s origins—in part—predate the Declaration of Independence, and therefore the United States itself. As Franklin was Postmaster under the Continental Congress and was George Washington’s first Postmaster, his system continued.
 
Smithsonian National Postal Museum
POSTAL INSPECTORS:
THE SILENT SERVICE
An Exhibit at the Smithsonian National Postal Museum
Mail connects families and friends, businesses and customers, government and citizens. It carries information, goods and valuables into our homes and offices. For that reason, scam artists and criminals have long been tempted to use the mail for illegal means. Protecting the mail and the postal system is the job of the U.S. Postal Inspection Service. Sometimes called the silent service, it is one of the oldest federal law enforcement agencies in the country.
   
Google News Archive
10 November 1973, Reading (PA) Eagle, pg. 4, col. 2:
“Silent Service”
now makes bid
for recognition

(...)
Q. If the service is so hot, how come nobody ever heard of it?
A. For years they have been known as the “Silent Service” and prided themselves on anonymity. Now they’re not adverse to publicity but because of their long tradition of staying out of the limelight, nobody pays any attention to them.
 
18 May 1980 Beaver County Times (PA), “Postal inspector takes pride in cracking frauds” by Rena A. Papale, pg. B1, col. 1:
For 200 years, the postal inspection service has been known as the silent service, avoiding publicity.
     
OCLC WorldCat record
The silent service : U.S. submarines in World War II
Author: Hughston E Lowder
Publisher: Baltimore, Md. : Silent Service Books, ©1987
Edition/Format:  Book : English : 1st ed
 
Google Books
Encyclopedia of Security Management:
Techniques & Technology

By John Fay
Boston, MA: Butterworth-Heinemann
1993
Pg. 560:
Although small compared to other agencies, the Postal Inspection Service has always been very proud of its accomplishments and place in American history. Unofficially nicknamed “The Silent Service,” the Inspection Service has been involved in many prominent and successful investigations over the years.
 
New York (NY) Times
MEDIA; Makeover: The Postal Service Goes Hollywood
By BILL CARTER
Published: March 29, 1999
(...)
As to the obvious question: What exciting adventures of postal workers? Mr. Weideman had a surprising answer: ‘‘The most elite law enforcement agency in the country, one nobody really knows about, is the Postal Inspection Service. I made a deal with the Post Office for rights to their stories.’‘
 
The result: ‘‘The Inspectors,’’ a movie, starring the Oscar-winner Louis Gossett Jr., which played on Showtime last September, scoring the best ratings for any original film in that channel’s history.
(...)
He learned that the service was Efrem Zimbalist Jr.‘s first choice for a television series in the 1970’s.
 
’‘He and the producer Quinn Martin approached the Post Office, looking to do a show about postal inspectors,’’ Mr. Weideman said. ‘‘I saw the letter they wrote. But postal inspectors liked to be known as the ‘silent service’ back then. They turned them down. So Zimbalist went across the street to the F.B.I.’‘
 
OCLC WorldCat record
Postal inspectors : the silence service : an exhibit at the Smithsonian National Postal Museum, February 7, 2007 - February 28, 2009
Author: National Postal Museum (U.S.)
Publisher: [S.l. : s.n., 200-]-
Edition/Format:  Computer file : English
Summary: Mail is the connecting force between families and friends, businesses and customers, government and citizens. As much as it does for the good, it also carried along a great deal of crime. Scam artists and criminals have long been tempted to use the mail for illegal means. This Web site is an online companion to an exhibit that explores the job of the U.S. Postal Inspection Service. Here visitors can see why although it may be referred to as the “silent service,” it is one of the oldest federal law enforcement agencies in the country