 These vehicles are identified by a seven-digit number displayed on the front and rear.The Department of Defense and the USPS jointly operate a postal system to deliver mail for the military; this is known as the Army Post Office (for Army and Air Force postal facilities) and the Fleet Post Office (for Navy, Marine Corps, and Coast Guard postal facilities).In February 2013, the Postal Service announced that on Saturdays it would only deliver packages, mail-order medicines, Priority Mail, and Express Mail, effective August 10, 2013.