USPS Mail Delivery Vehicles are 25-30 years old and use engines designed in the 1970’s that get 10 MPG.
According to the USPS, if you ever receive unsolicited merchandise in the mail it is yours to freely keep. It is also considered a rare instance where “finders, keepers” applies unconditionally.
When famed jeweler Harry Winston donated the 45 carat Hope Diamond, valued at $200 to $250 million USD, to the Smithsonian, he simply shipped it via the US Postal Service in a box wrapped in brown paper.
In 1959 the USPS attempted to deliver mail via cruise missile and successfully shipped 3,000 pieces of mail from Virginia to Florida in 22 minutes.
The mail truck most commonly used by the USPS was produced by Grumman and is called the Long Life Vehicle. Production began in 1987, and a new one hasn’t been produced since 1994.
The US Postal Service still uses Mule Trains to deliver to 2 places: Supai and Phantom Ranch, Arizona