Beating at 36,000 vibrations per hour, the El Primero caliber is a true marvel of engineering and innovation. Its performance was so impressive that Zenith supplied the movement to other major brands such as Rolex, Movado, and Ebel throughout the 1980s and 1990s. Yet the story nearly ended in 1976, when Zenith’s management became convinced that quartz technology was the future and decided to dispose of all the tools and materials required to produce the El Primero.