In 1965 Rolex introduced the screw-down chronograph with the reference 6240 known also as the “Oyster” Daytona with a metal link bracelet. The purpose of the screw-down feature was to provide a better water resistance capability without damaging the watch movement.
In 1987 there were some minor variations to the Rolex Daytona. One of the updates of this timepiece was due to the manual winding of the “Valjoux caliber 72”