Zenith Defy El Primero 21 49.9000.9004/78.M9000 - Serial #367949 (Pre-Owned)An engineering marvel from one of the most important names in chronographs, the Zenith Defy El Primero 21 employs two independent escapements, the first of which for the time of day running at 36,000 BPH and the second for the chronograph which runs at an astonishing 360,000 BPH!!! Due to the insanely high 50 Hz beat rate of the chronograph a 50 hour power reserve indicator is placed on the dial. When the reserve appears low you can manually power the