World Explorer The GMT-Master was originally developed for airline pilots and frequent travellers. With its dual time zone functionality and robust design, it remains a trusted companion for those crossing time zones. Classic Functionality This 1998 reference 16700LN features a 40mm case with a black dial and rotatable bezel marked for 24-hour tracking. Powered by the calibre 3175 automatic movement with a 48-hour power reserve, it includes an Oyster bracelet secured by an Oysterlock clasp. A vintage-inspired travel watch with enduring appeal.