Crown

The British Horological Institute (a professional horological body, not a standards authority) defines the component in the glossary of its Practical Clock and Watch Servicing Distance Learning Course Technician Grade, under the headword "Button": "The external component of a watch used to wind the watch and set the hands to time. Also called the crown." Two jobs, winding and setting, in one part that the wearer is the only person who ever touches deliberately.

On a sealed watch the crown is also a stopper. Rolex's own account of its Oyster case states that "A system of screwing down the bezel, case back and winding crown against the middle case ensured that the case was hermetically sealed", and records its later work in the company's own words: "In 1953, Rolex introduced the Twinlock winding crown, which incorporated a patented system with a double seal", followed in 1970 by "the Triplock winding crown, comprising an additional sealed zone". Omega, writing about its own watches, states the consequence for an owner plainly: "If your watch is equipped with a screw-in crown, always screw it in after handling it."

The Swiss industry norms the part without publishing the definition. The Federation of the Swiss Watch Industry's list of available NIHS standards, valid from April 2026, includes NIHSG 63-01, Couronnes, tubes de couronnes, poussoirs latéraux pour montres, correcteurs latéraux pour montres – Terminologie, a terminology norm covering crowns and crown tubes, first issued in 1967 and revised in 2022. The list gives titles only, so no definition text was read here.