Watchuwant is now WatchBox! Subscribe to our channels for the best luxury watch content. The Rolex Cosmograph Daytona has been around long enough to look back on a glorious history of iconic models, moments, and movements. No Rolex Daytona movement has given rise to greater legend or lust than the 1988-1999 Zenith El Primero, modified as the Rolex Cal. 4030. Inside this 40mm 18-karat yellow gold Rolex Cosmograph Daytona, the El Primero beats like the heart of a champion. As the first generation of automatic-winding Rolex Daytona, the 16520 of 1988 ushered in the era of the watch enthusiasts know today. The days of plastic bezels, plastic crystals, 37mm cases, and fragile manual wind movements were over; the era of crown guards, engraved metal bezels, and sapphire crystals had begun. With a burly 40mm case enhanced by crown guards and screw-down pushers exclusively, the 1988 Daytona proved so right from square one that it’s appearance has scarcely changed in 27 years. So timeless is the look that nearly 30 years later, a well-maintained 165XX generation Daytona remains almost indistinguishable from the 2015 models. Inside the 18-karat yellow gold case lies the main event. Zenith-built, Rolex-specified caliber 4030 automatic movement keeps the time in COSC-chronometer fashion for a power reserve of 52 hours. In 1988, Rolex wanted to best automatic chronograph movement in the world for its commercially pivotal re-launch of the Cosmograph Daytona. Zenith of Le Locle delivered. A true connoisseur’s secret and complete manufacture, Zenith constructed the caliber 4030 to Rolex’s exacting specifications. Rolex took the El Primero – history’s first integrated automatic chronograph caliber – and hot-rodded it. Out went the mobile adjusting index; in went the Rolex free-sprung balance. Out went the conventional balance wheel; in went the Rolex Microstella balance. Out went the high-maintenance Zenith winding click wheel and its springs; in went the bulletproof Rolex replacement. Finally, the already reliable Zenith 5hz escapement was re-tuned to 4hz, because “reliable” isn’t reliable enough for the five-point coronet. Naturally, the El Primero’s date was binned in order to preserve the balanced simplicity of the Daytona’s dial. While every example of the Zenith-powered generation of Rolex Cosmograph Daytona is scarce in comparison to the Rolex in-house models that followed, solid gold examples on a full bracelet are exceptionally special pieces. With in-house metallurgy research and its own foundry, Rolex is able to create its own 18-karat gold cases, bezels, and bracelets. The quality of the metalwork speaks for itself, and it carries an additional bonus; although the stainless steel Rolex Daytona did not receive solid bracelet end links until the final model year in 1999, all solid gold examples features these premium components from the very onset of production. As a result, the full gold bracelet of the Cosmograph Daytona 16528 looks and feels more like a 2015 example than its steel contemporaries; the hollow end-link “Rolex rattle” is absent. See this living legend, the Rolex Cosmograph Daytona 16528, in high-resolution images at www.thewatchbox.com Video and content by Tim Mosso.