This iron key comes from the wreck of the 1622 galleon Nuestra Señora de Atocha. Though the lock it went to is not known, the key’s design shows it was for a warded lock, a type that uses internal obstructions called wards for security. How it worked: When the key was inserted in the keyhole, the hollow nose fit over a post inside the lock. This allowed the key to rotate from a fixed point. A series of wards, or obstacles, were set around this pivot point. Notches cut into the bit, or blade, of the key corresponded to the wards and allowed the key to rotate past them. Once past the wards, the bit could then tip a lever or slide a bolt to disengage the locking mechanism.