The Automatic Chrnograph
From Chronopedia
The Automatic Chronograph
While automatic watches from the other groups used a simpler modular, cam-actuated movement, Zenith opted for a more complex but much smoother column wheel movement and used a fully integrated design. The El Primero had a 36,000 vph high-beat movement that not only had a second hand with an appealingly smooth motion, but could record time within 1/10 of a second as well. Today the El Primero continues production as one of the very few high-beat chronographs on the market, and remains one of the most advanced chronograph movements of all time.
Interesting faxt: The El Primero also found its way into another watch icon - The Rolex Daytona.