The Rolex Daytona reference 16520 is a landmark chronograph, introduced in 1988 as the first automatic Daytona, powered by the Zenith‑based Caliber 4030. Its 40 mm stainless steel case, measuring approximately 47 mm lug‑to‑lug and around 12.5 mm thick, marked a modern evolution of the Daytona line. The Caliber 4030, a heavily modified Zenith El Primero, features a 12‑hour chronograph and robust 31‑jewel automatic movement, offering a 40‑ to 54‑hour power reserve depending on the source. With 100 m water resistance, screw‑down pushers, and a sapphire crystal, this reference blends vintage charm with practical durability. Produced until around 2000, the 16520 sits at the intersection of Rolex’s historic chronograph lineage and the transition to fully in‑house movements, making it a highly collectible and historically significant piece. U serial (circa 1998). Excellent Condition with European Watch Company leather pouch.