Graham Watch Fortress GMT Green 2FOBC.G01A. The Fortress GMT is equipped with a mechanism for correcting the hour hand by means of the crown (patented mechanism). Located on the left side of the case, the pusher has been completely redesigned to become the only pusher allowing the hour hand to be moved by 1 hour. This makes it easy to update the time while on the move. Each Graham watch is water tested to 300 feet (100 meters/10atm). This model has a GMT hand that allows the second time zone to be read simultaneously. This provides a technical answer for people who travel constantly, juggling time zones. In order to standardise the measurement of time in all countries, the earth has been divided into 24 time zones, the first of which is crossed by the Greenwich meridian and is considered the prime meridian. From this central point, 12 time zones were defined running westwards from -11 to 0 (0 = GMT - centre of the time zones) and a further 12 from +1 to +12 eastwards. GRAHAM has developed one of the simplest GMTs in the world, allowing you to set your watch without ever using the crown.