What does the reference number on your rolex mean?

The reference number on a Rolex refers to the model of the watch. Typically the reference number only changes when major changes are introduced to the watch. If only minor changes are made a "1" is added to the beginning of the old reference. So in the early 2000s when the 14270 Explorer was remodeled only slightly it became the 114270. Major changes such as the introduction of a larger case or major cosmetic differences will result in a totally new reference number all together.

It is also noted the serial number on a Rolex, found between the lugs, is unique to each watch and is currently preceded by a letter. The serial number can only be seen if the watch bracelet is removed.