The Rolex Cosmograph Daytona, one of the most popular luxury watches on the planet, turns 60 years old this year. How has this iconic chronograph evolved over the years? Surprisingly, unlike many other Rolex models, today's Daytona is aesthetically and mechanically very different from when it started. Another important change is that the Cosmograph Daytona was once one of Rolex's slowest-selling models, which is quite shocking considering its immense popularity today. So to mark the 60th birthday of this famous chronograph, let's take a deeper look into the history and evolution of the Rolex Daytona.  The first replica Rolex Daytona watch was the reference 6239. it had a compact 37.5 mm case, a metal bezel engraved with a tachymetric scale, a pair of pump pushers on either side of the winding crown, three counters on the dial, and an Oyster bracelet. What's more, the case houses a hand-wound Valjoux-based movement. That's right, the vintage Rolex Daytona with a four-digit reference number is a hand-wound chronograph. And in 1971, Rolex introduced two of the oldest hand-wound Daytona models, the 6265 (metal bezel) and the 6263 (acrylic bezel). These two now classic Rolex Daytona watches brought together the best of all previous models and a few new updates. They feature a screw-down chronograph pusher, an Oyster case with Triplock winding crown, and a high-beat manual winding movement. Another important moment in the evolution of the Rolex Daytona came in 2000, when the company switched to the in-house 4130 movement. Unlike its predecessors, the Valjoux and Zenith movements, the 4130 movement is an automatic chronograph movement entirely developed and manufactured by Rolex. Another notable update to the Daytona line is the addition of the Oysterflex strap, Rolex's version of a black rubber strap with a metal blade in the center (which is why it is called a bracelet and not a strap). Rolex eventually replaced all leather strap variants with Daytona watches with Oysterflex bracelets. The evolution of the Rolex forum has seen more than its fair share of major changes over the past six decades. It was once a company bust, and today it is one of the fastest-selling Rolex watches. This famous chronograph continues its winning ways, from changes in movement and case size to more material options and bracelet styles.