The Rolex Cosmograph Daytona 116520 is one of the most significant references in modern Rolex history, and this 2000 example dates to the very first year of production. Released in 2000 as the successor to the 16520, the 116520 introduced Rolex's first-ever in-house chronograph movement — the Caliber 4130 — replacing the modified Zenith El Primero that had powered the Daytona since 1988. A first-year piece carries the rare distinction of being among the earliest Daytonas ever produced with a Rolex-manufactured chronograph movement, a turning point that reshaped the brand's relationship to its most coveted sports model. The 40mm Oystersteel case is finished with the polished steel tachymeter bezel that defined the 116520 generation through its 2016 discontinuation, with the screw-down Triplock crown and screw-down chronograph pushers preserving 100-meter water resistance. Applied luminous hour markers and three contrasting subdials at 3, 6, and 9 deliver the layout that has been the Daytona's visual signature for decades. Caliber 4130 is a column-wheel, vertical-clutch automatic chronograph composed of 290 parts and 44 jewels, beating at 28,800 vibrations per hour with a 72-hour power reserve and Superlative Chronometer certification. Sapphire crystal, water resistant to 100 meters, on the Oyster bracelet. Pre-owned, 2000 first-year example.