Laser coronet
Picture of a laser coronet
In 2002 Rolex introduced a new security characteristic, because counterfeits were getting better and better: the laser coronet in the sapphire crystal. This laser coronet is at the lower edge of the crystal at 6 o'clock position and is so small that one can hardly see it with the naked eye. It can be found most simply if you take a look from the opposite side with strong oblique light directed upon the crystal. Usually only a small mark on the crystal can be seen, which, viewed with the help of a magnifying crystal or loupe, becomes a coronet.
A laser coronet with an additional "S" means that the crystal was exchanged during a service
(source: Sloth, RLX forum)
However, the introduction of the laser coronet was done step by step. It was not introduced for all models at the same time. It was introduced first in the Air King, Submariner (without date), Explorer and Daytona models. Other models followed with the Y series (autumn 2002). Other sources report that the introduction lasted until the end of 2003, perhaps even until the beginning of 2004. If you buy a new Rolex now the laser coronet can be found on every watch. Watches manufactured between 2002 and the beginning of 2004 can possess this security characteristic, but depending on the model reference, it may not be present.
Corroded Counterfeitkrone
(source: Hannes, RLX forum)
With an exchange of the sapphire crystal this laser coronet is present in the new crystal. The coronet looks however slightly different: Within the laser coronet there is an additional "S" lasered (s means changed by service).
Although Rolex introduced the laser coronet as new security characteristic, it did not take long to find counterfeits with a coronet in the crystal.
At this time it is "only" a corroded or etched coronet with a thicker, more constant structure as a result. You can recognize these with the naked eye easily and therefore it is quite easy to expose a counterfeit. However, it is only a question of time when better laser coronets occur in the counterfeit market and the laser coronet on its own is no 100% identification of a genuine watch.