What does “Crown” mean?

The crown is the knob on the side of the case used to wind the movement and set the time and, on many watches, the date. A screw-down crown screws onto a threaded tube in the case to seal it, which greatly improves water resistance; it must be unscrewed before winding or setting. Rolex's screw-down systems are known as Twinlock and Triplock, and markings below the Rolex coronet on the crown show which one is fitted.

For dealers, the crown is part of both condition and originality checks. It should screw down smoothly and fully, wind without grinding and set positively, and its tube shouldn't be damaged. The crown's style and markings should be right for the reference and era: replacement crowns fitted during service are normal, but an incorrect one can lower value. Always make sure a screw-down crown is screwed down fully before the watch goes near water.

Example: 'Crown screws down correctly, winds smoothly, Triplock.'