" At First, these wristwatches had been a single-off or custom creations That always seemed a good deal just like the pocket watches from which they developed. But soon, wristwatches took on their own aesthetic, with their own individual technical innovations to unravel new problems presented by wrist-borne timekeepers. Hublot’s https://www.watchesworld.com/a-history-of-watch-reference-numbers/