The number of chronometers certified by the COSC (Switzerland’s official chronometer testing institute) increased by almost one third year-on-year in 2011, with Rolex once again accounting for the lion’s share of chronometer certificates.

Rolex produced 751,285 chronometers, split roughly into two-thirds for watches with calibres greater than 20mm in diameter (i.e. gents’ watches) and one-third for calibres with a diameter of less than 20mm (ladies’ watches).

Despite Rolex’s nearest competitor, Omega, increasing its chronometer production almost by half (+48.6 per cent at 509,301 units) year-on-year, the Bienne-based flagship brand of the Swatch Group still lags its rival by around one third.

The rest of the field trails at ever larger intervals, starting with Breitling in third place (154,456). Interestingly, Breitling is one of only two brands to submit quartz watches for chronometer certification last year.

^* Figures from the 2011 annual COSC annual report