Someone using the Huge Cajones mailer wrote: David Lesher <wb8foz@nrk.com> writes:

USPS uses key locks seemingly designed by Ben Franklin himself. Look at them someday. FedEx boxes used to have Simplex 926 5 pushbutton ""locks"" if you stretch the point.

Still did last I checked. Don't let the old-fashioned look deceive you. Most mail storage boxes use lever tumbler locks (similar to what's used in safe deposit vaults, though obviously the mailbox locks have a flimsier plug). How is that obvious? Safe deposit locks generally aren't designed to be hard to open, just hard to open without damage. There's always either a guard or a locked vault door protecting the locks. Mailboxes, on the other hand, generally aren't kept under guard or in vaults.