"Sigma" Dials

In the 1970s, a group of Swiss watchmakers and experts decided to make the presence of gold on dials official. In the same way that C.O.S.C. certification was born, these experts decided to use the Greek letter Sigma. This marking could be present on the dial, the bracelet or even the case back. Because they are used for relatively short periods of time and on a limited number of models, Rolex and Patek Philippe models with “Sigma” dials are particularly sought-after by collectors.