Zenith El Primero watches

Zenith El Primero is the name of a movement and of the chronographs built around it. Zenith unveiled the calibre on 10 January 1969 as the 3019 PHC, an integrated automatic chronograph beating at 36,000 vibrations per hour (5 Hz), fast enough to time events to a tenth of a second. It was the first high-frequency automatic chronograph movement.

The El Primero survived because Charles Vermot hid the equipment needed to make it in the attic of Zenith's Ponts-de-Martel facility. Rolex later used a specially modified El Primero in the Daytona from 1988 to 2000. In 2003 Zenith opened up the dial of the Chronomaster Open, with a cut-out over the escape wheel and balance. The Striking 10th calibre 4052 followed in 2010, built to display tenths of a second, and for the movement's 50th anniversary in 2019 Zenith unveiled the calibre 3600, with a 60-hour power reserve.

The heart of the family is the Chronomaster, in 38 and 42 mm steel or rose gold, often two-tone, with silver, blue, grey or black dials. The Open versions show the escapement through the dial, the Full Open models are skeletonised, and the Grande Date carries a big date in a 46 mm case. The 2022 Chronomaster Open is a 39.5 mm watch on the calibre 3604, an adaptation of the 3600. Around the Chronomaster sit the 45 mm Stratos Flyback, the Striking 10th, the 40 mm Synopsis, the Rattrapante, the Tourbillon, the Winsor Annual Calendar and the Doublematic, and cases in titanium, aluminium, ceramic and carbon join the steel and gold.

Limited runs include a 45 mm titanium Chronomaster 1969 Tribute to the Rolling Stones of 1,000 pieces and the El Primero Sport Land Rover BAR team edition of 250. Zenith writes the calibre into the middle of the reference: the Striking 10th references carry 4052, the 2022 Chronomaster Open references 3604.