Early Races were generally timed by stopwatches mounted to vehicle dashboards, but as the complication was shrunk, they have been additional frequently noticed on wrists, particularly in the F1 and endurance racing heyday in between the ’50s and ’70s. Influenced by British pilot’s watches through the seventies, Hamilton’s Khaki Aviation https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/