Part of the fun of getting into the vintage Rolex collecting game is discovering all the various design details. And many of these details can be found on the watch dials. Today we explore the origins of the Rolex Sigma dial and what that can mean for the value of a vintage Rolex watch.
The Sigma Symbol and APRIOR
In the 1970s, a group of Swiss watchmakers who were part of the L’Association pour la Promotion Industrielle de l’Or or APIOR (which translates to The Association for the Industrial Promotion of Gold) formed an official initiative to highlight the use of gold on watches.
Similar to how the “Chronometer” designation was controlled and guaranteed by Contrôle Officiel Suisse des Chronomètres (COSC) to denote optimal timekeeping precision, APRIOR wanted to formalize how watchmakers signified the use of precious gold in watches – especially important on steel watches since stainless steel and white gold are similar in color.
The symbol chosen was the Greek letter Sigma: σ. According to a US Patent Office Registration Certificate (filed in August 1971 and registered in July 1972) the σ mark “certifies that the goods are of Swiss origin and contain solid gold up to a certain standard as established by the Swiss statutory requirements concerning the control of the use of gold and meet standards and quality established by the applicant.” It also mentions that the mark was “First used February 25, 1970; in commerce on or about Mar. 1, 1970.”
The Sigma mark could be used on the dial, bracelet, or caseback of watches to signify the presence of gold. Some famous watch brands that used the APRIOR Sigma mark included Patek Philippe, Vacheron Constantin, IWC, and of course, Rolex.
Rolex and the Sigma Dial
Sigma dials can be found on Rolex watches dating from the early 1970s until the latter part of the decade; however they can sometimes be found on Rolex watches from the late 1960s, as the “Sigma” symbol was being used by certain dial manufacturers before it became officially adopted in the early 1970s . Rolex Sigma dials have two σ marks surrounding the “T SWISS T” signature just under 6 o’clock marker on the dial (“T” refers to the use of tritium as luminescence on the dial). Therefore, Rolex Sigma dials denote that the hand-applied indexes and hands are craft from 18k gold.
Rolex Sigma dials are more often found on stainless steel models (as a way to differentiate between the steel case and bracelet and white gold details on the dial); however there are also examples of the Sigma dial on two-tone and yellow gold Rolex models.
We have seen Rolex Sigma dials on vintage Daytona, Date, Datejust, Day-Date, and Cellini watches. You will not find Sigma dials on models like the Submariner, Sea-Dweller, or Explorer from the same era since Rolex did not have gold surrounds around the painted tritium hour markers at that time.
Since Rolex only used the Sigma dial for a handful of years in the 1970s, it comes as no surprise that the small σ markings can add to the value of a vintage Rolex watches. Today, vintage Rolex Daytona chronographs with Sigma dials are particularly collectible, and run a premium when they surface at auction.