Signed Rolex, Oyster Perpetual, Cosmograph, Daytona, Ref. 16520, Case No. W449241, Circa 1994

Rolex Daytona models had been in production for twenty years until the firm produced the reference 16520 in 1988 with an automatic movement. The movement in this new self-winding Daytona was based on the Zenith Caliber 400 which was a celebrated movement and the industry's only self-winding chronograph movement that met Rolex's high quality standards. Although it was a movement that met standards, Rolex decided to improve on it and modified the caliber to its own specification including a new larger escapement, freely sprung balance and balance spring with Breguet overcoil (which was a more costly configuration that lead to higher accuracy). The balance oscillation rate was reduced allowing for a less frequent watch service and the date function was eliminated. Retaining just 50% of the Zenith movement, the final result was the caliber 4030 which was used in modern Daytonas until 2000, at which time Rolex introduced the reference 116520 with the new and fully in-house caliber 4130.

The 16520 models had dials which went under a transformation due to oxidation where the chapter rings around the subsidiary dials changed color from white to a shade of brown. These Compax Marrone or Brown Compax models, as they are nicknamed, occurred on watches that were produced in the 1990's, and watches that have the upside down 6 digit on the 12 hour register. Color-change or "tropical" dials are extremely sought after as they are usually attributed to small production runs. Once the firm realized that the dials would change color, it was seen as a defect and consequently the material used was changed in hopes of finding a solution. Pieces with a small production are rare and those with a color-change dial are even rarer making the present Brown Compax a very special timepiece.

Reference 16520 is illustrated in 100 Years of Rolex by F. & G. Mondani, 2008, p. 205.