The concept of a combination lock was first presented by the Egyptians, which was found in the ruins of the ancient Palace of Khorsabad in Niveveh (built in 704 BC). This invention was created by multiple sticks of wood, each of which was positioned at a different length so that it fit perfectly into an individualized slot at the bottom of the contraption.
Enough room was left for a specialized key to fit among the wooden sticks, lifting them into leveled holes on the opposite side of the device. This allowed the door to the palace to be opened.
First Metal Locks
The Romans claimed the earliest ideas of metal combination locks. Furthering the Egyptian principles, they replaced the wooden pins with metal ones.
Usually, the keyholes were eloquent shapes, designs, or animals. This made them difficult to replicate, thus preventing lock picking.
Another important feature of Roman locks was the Ward Lock, which (by means of subdivisions surrounding the hole) prevents improper keys from fitting into the keyhole.
Advanced Combination Locks
Linus Yale Jr. of Shelburne Falls, Massachusetts coined the bank lock in 1851.
From there, he went on to invent the Yale Magic Bank Lock, Yale Double Treasury Bank Lock, and Cylinder Lock. Of these, the Cylinder Lock (based on the original Egyptian design) has been most widely revolutionalized, as its design serves as the basis for many of the simpler combination locks today.
Modern Combination Locks
The majority of combination locks are based off of the Pin Tumber or Ward designs. Typically, multiple numbers or letters will form a combination to open the lock.
The idea for such a design was originally recorded by Gerolamo Cardano of Italy in the 1500s.
Improvements of the Modern Combination Lock
Joseph Loch of Germany created the first "modern" combination lock in 1878 for Tiffany's Jewelers in New York City. While doing so, and for the next 20 years, Loch focused on improvements within the tumblers to provide maximal security and minimal deception.