A 9-linge Model with a cover to safeguard the crystal (a little an obsession at the time, as we’ll see), the look didn’t quite get off and they are exceptionally rare and very highly-priced. Though not as much of a household name as Rolex, Potentially, Audemars Piguet features something else https://www.watchesworld.com/a-history-of-watch-reference-numbers/