Daytona 116520 (2000-2016)

The 116520 was the first steel Daytona powered by Rolex's own automatic chronograph movement. It arrived in 2000, replacing the Zenith-derived mechanism of the previous generation. From the front, it looked like a modest revision of an established racing watch. Inside, it marked a much larger change.

Rolex had used an extensively modified Zenith El Primero as calibre 4030 in the automatic Daytona since 1988. The new 4130 was designed by Rolex around a different arrangement of parts, including a vertical clutch for the stopwatch. This couples the chronograph through contact between surfaces rather than by bringing a toothed wheel sideways into mesh.

The change also moved the ordinary seconds display to six o'clock and the elapsed-hours display to nine. The two upper counters sit slightly above the dial's centerline. These are small visual consequences of a new mechanism, not simply a graphic designer deciding to rearrange three circles.

The 40-millimeter steel case retains a polished metal bezel engraved with the tachymeter scale used to calculate average speed. White and black dials give the same parts very different contrast. In either version, the bezel joins the case as one continuous metal outline; there is no dark ceramic border around the face.

That makes it a useful counterpart to the 2016 ceramic Daytona, which kept the 4130. The earlier watch contains the important movement change; the later one makes the more conspicuous change to its appearance.