1mm. When AP promoted the watch as “More-Thin,” enthusiasts continued to make reference to it as “Jumbo” supplied its 39mm scenario. Other slight improvements involved a switch from a white date wheel to the black Variation 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/