In most watches that housed this now-famous movement, however, the dial was not designed to actually record these minuscule measurements in an easily legible way. The El Primero would become the cornerstone upon which Zenith would build its modern brand for many years to come. In 1969, Zenith made history with the introduction of the original El Primero caliber, which was notable for, among other aspects, its uncommonly high frequency of 36,600 vph (5 Hz), which in practical terms meant that its integrated chronograph could record elapsed times not just to the second but to the 1/10th second. The Le Locle-based manufacture still holds the world record for chronometry Observatory Prizes, at 1,565. Zenith has always been all about pushing the boundaries of mechanical timekeeping precision.

Zenith Chronomaster Sport on steel bracelet In this feature from the WatchTime archives, I give it a test drive. Zenith’s most attention-grabbing release of 2021 was the Chronomaster Sport, whose revolutionary 1/10th-second chronograph display is intended to lead the El Primero-equipped series into the future.

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