The Zenith El Primero is one of the most iconic chronographs in watchmaking history. First released in 1969, it was the first integrated automatic chronograph movement, making it a significant milestone in Zenith's history and watchmaking. The El Primero operates at a high frequency, allowing it to measure short time intervals to 1/10th of a second. It is known for its distinctive style, featuring a tri-color subdial configuration, and a reputation for precision and reliability.