GMT-Master II

The GMT-Master was made to display two times at once. Introduced in 1955 during the expansion of long-distance air travel, it added a hand that circled the dial once every twenty-four hours and a rotating ring marked with a twenty-four-hour scale. An ordinary hour hand could show local time while the extra hand gave a second reference.

The GMT-Master II improved the arrangement in 1982. Its local hour hand could be moved independently, one hour at a time, without stopping the watch or disturbing the minute and twenty-four-hour hands. Changing local time no longer required resetting everything.

The colored ring is therefore a scale, not just decoration. Two colors divide the twenty-four hours into halves, making it easier to distinguish daytime and nighttime on that second time display. Rotating the ring lets the wearer read a different offset against the same extra hand.

The 16710 belongs to the aluminum-insert generation. It came with red-and-blue, red-and-black or black inserts and a comparatively slim steel case. The later 116710 generation brought ceramic inserts and a broader case design. In 2013 the blue-and-black BLNR made two colors possible in a single ceramic component.

These changes are conspicuous in photographs, but the independent local hour is the family's more consequential feature. A 16710 and a blue-black 116710BLNR look different and use different movements. Both make the same practical distinction between the place where the wearer is and the time they want to keep track of elsewhere.