Longines Ultra-Chron Diver (1968) 7970-15385823

In 1967, Longines drew a sporty version of the Ultra-Chron: a diver’s watch with a bright-red minute hand, water-resistant to 200 meters. In early 1968, it was the first high-frequency diving watch, and probably the most accurate. Ultra-Chron stands for Ultra-Chronometer, which means this watch was more accurate than a Chronometer. Longines guaranteed an accuracy of one minute a month, which transforms to two seconds a day. The tonneau-shaped watch was fitted with a calendar mechanism and a turning bezel, which enabled divers to determine their immersion time. To be able to read the time even in murky water, the index marks on the dial hand, the triangle on the bezel were filled with tritium. 

The Ultra-Chron was the last mechanical watch in horological history to match the accuracy of the electronic watch (at that time with a tuning-fork movement), but with the advantage that no battery was necessary. Technically the Ultra-Chron draw its inspiration from the Longines Observatory Chronometer, the Calibre 360. This watch that set new records in terms of accuracy (around 1/10 of a second per day) and represented in 1959 the world’s first high-frequency movement for a wristwatch, vibrating at 36,000 bph. Longines looks back on more than 100 years of experience in working with high-beat movements for the official timing of sport events all over the world.