The Rolex Cosmograph Daytona, first introduced to the market in 1963, is one of the most renowned chronographs in the world and holds a deep connection to the realm of motorsports. Initially designed as a manual-wind chronograph for race car drivers and simply known as the Cosmograph, Rolex later renamed the watch in 1965 to honor the official timekeeper of the famous NASCAR race in Daytona. For a long time, the watch was considered a niche product in the Rolex catalog and was sold in relatively limited quantities until the release of the first self-winding Daytona in 1988. From then on, the interest in the model dramatically increased and soared even higher when newer references were introduced.

This surge in popularity also led to a boom in sales of vintage Daytona references, with collectors paying astonishing sums for pieces with good provenance. The peak of Daytona frenzy was reached in 2017 when a reference 6239 owned by actor Paul Newman became the most expensive wristwatch ever sold, fetching a record-breaking $17.8 million. Since that sale, the popularity of the Rolex Daytona has shown no signs of slowing down.

The 16520 was the first automatic Daytona, and inside it beats a modified Zenith El Primero movement. Yep, Rolex took the legendary high-frequency chronograph from Zenith, slowed it down a notch for reliability, swapped out a bunch of parts (some say over 50), and turned it into the Caliber 4030.

So while the dial says Rolex, the heartbeat comes from one of the most iconic chronograph calibers ever made. It’s basically the Daytona that bridged the gap between vintage hand-wound and modern in-house models – a bit of a legend in its own right.