1mm. Even though AP promoted the watch as “More-Thin,” enthusiasts ongoing to consult with it as “Jumbo” supplied its 39mm case. Other slight modifications involved a switch from a white day wheel to a black version to the blue and black dials as well as addition of a double-deployant clasp https://www.watchesworld.com/a-guide-to-10-of-the-best-dress-watches/