Originally launched in 1967 with the groundbreaking Caliber 431, one of the first series-produced movements operating at five Hertz, the Longines Ultra-Chron has long been synonymous with high-beat precision. The brand’s mastery of high-beat movements, however, began even earlier. In 1910, Longines patented a stopwatch capable of measuring to 1/10th of a second and operating at a frequency of 5 Hz – or 10 times a second. The new Ultra-Chron Classic carries forward this heritage, now powered by automatic high-frequency Caliber L836.6, introduced in 2022 and chronometer-certified. This movement runs at 36,000 vibrations per hour, incorporates an anti-magnetic silicon balance spring, and offers a comfortable 52-hour power reserve. The Ultra-Chron Classic’s precision credentials extend beyond traditional chronometer standards. Unlike most conventional certification processes, which test only the movement, this timepiece achieves full chronometer certification from the Geneva Chronometric Observatoryrepresented by the TIMELAB foundation. In keeping with the ISO 3159 standard, the qualification process subjects the finished watch to a rigorous 15-day testing period, during which the entire assembled timepiece undergoes functional tests in various positions at three different temperatures—8°C, 23°C, and 38°C—to verify its accuracy.