"An Useful guide on the heritage of British watchmaking. Horology enthusiasts of all concentrations are sure to find value here." The third big phase transpired within the early 1900’s. The form of the timekeeping equipment changed in favor from the wristwatch. The main chronometer wristwatch movement arrived in about 1910, https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/