"An Enlightening guidebook around the heritage of British watchmaking. Horology admirers of all degrees are certain to locate worth here." The 3rd big move occurred in the early 1900’s. The form with the timekeeping equipment adjusted in favor of your wristwatch. The main chronometer wristwatch movement arrived in about 1910, https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/