The Submariner bezel is marked in dive watch fashion: it shows 60-minute graduations, broken down into 5-minute increments, with numbers for each ten minutes. You’ll notice too that the first 15 minutes have one-minute tick marks indicated. These were made for divers to monitor their time underwater accurately.
The GMT-Master II, meanwhile, is marked by 24 one-hour increments, with numbers marking the even hours. This works together with the 24-hour hand in telling time in a second time zone.
Another small difference is that the Submariner has a luminous pearl on the bezel, at 12 o’clock. SEE ALL ROLEX >