The Rolex Cosmograph Daytona needs no introduction, it is probably the most recognisable and collectable Rolex of all time. However, it is sometimes forgotten that the Cosmograph Daytona model was a manually wound chronograph until the late 1980s. Up until then, the Daytona had been a rather niche wristwatch and by the 1980s it had become regarded as completely out of fashion. The model’s revival came in 1988 with the introduction of the automatic Cosmograph Daytona, it not only breathed new life into the model commercially for Rolex, but the attention it drew and its immediate popularity had the effect of boosting interest from collectors in the vintage Daytona models from the 1960s and 70s. The importance of the automatic Cosmograph Daytona cannot be underestimated, now over 30 years since its introduction, the automatic Daytona has itself become hugely desirable and sought after by collectors. The first reference of the new automatic was 16520, available in steel, all gold (reference 16528), and steel and gold (reference 16523), featuring a larger 40 mm. case that was, for the first time, made with crown guards. The model was available only with a solid metal tachymeter bezel and the crystals are sapphire crystal in place of acrylic for added scratch resistance. Interestingly, the movement was not an in-house Rolex movement but a heavily modified (with over 200 modifications) Zenith El Primero calibre 4030, which was the only one to meet Rolex’s exacting standards. Hence the model has become known generally as the ‘Zenith Daytona’. For the production of the reference 16520, certain dial design details changed, such as the use of a glossy finish and applied metal hour markers. As for the majority of Rolex models, the dials were slightly changed and improved over time, this has led to some rare variations being noticed by collectors that are now highly desirable. The most dramatic being the colour change subsidiary dials which can vary from light to dark brown and were caused by the degradation of the organic ‘Zapon’ coating on some dials made in 1994 and 1995. The famous ‘inverted 6’ dials from around 1993 are defined by the digit ‘6’ at 6 o’clock of the 12-hour subsidiary dial having the appearance of being upside down and therefore resembling a ‘9’ and the ‘Floating Cosmograph’ from the early production years are just some of the varieties available to the collector today. In 2000, a new replacement model for the reference 16520 was launched, the reference 116520, this time with a completely in-house movement, calibre 4130. Although similar to its predecessor, the new model had some changes including the positioning of the subsidiary dials which now had the seconds at 6 o’clock and the chronograph registers at 3 and 9 o’clock.