When Pan-Am first commissioned Rolex to develop a two timezone watch for the new Boeing 707 jets in 1956 , their concern was to keep the pilots reference to home time intact, while still allowing them to track the different time zones they travelled through. It was felt that keeping a home-time reference would alleviate jet-lag as the pilots could still keep their circadian routine. This also gave Jet Navigators an in-cockpit GMT time reference necessary for Celestial Navigation of the era.
Their efforts resulted in the GMT-Master ref. 6542. The GMT stood for Greenwich Mean Time, which was the world standard for a unified or universal time clock.
It's use in practice was initially envisioned as having the watch set for local time, and the bezel was rotated to the new timezone... Local was read at the dial and the timezone you were presently in would be displayed in 24hr time on the bezel....simple. When you got back home the bezel triangle should be back at the 12 o'clock position.
The New GMT and it's line soon became the "standard" and a pilots must-have time-piece. NASA test pilots were given GMT-Masters during development of the record breaking X-series jet aircraft, and they were the personal time-piece of many American astronauts.
The ref 16700 that was produced from about 1988 until 1999 was the last of those watches with synchronized 24hr and 12 hour hands, but with the upgraded sapphire crystal, hacking seconds, and quick-set date.
Specifications
Model: .........................GMT-Master
Reference Number: ........16700
Production Years: ..........1988-1999
Movement: ...................Caliber 3175
Power Reserve: .............48 Hours
Water Resistance: .........100m
Bezel:.......................... Bidirectional
Crown: ........................Screwdown Twinlock
Crystal:....................... Sapphire
Diameter: ....................40mm
Thickness: ...................N/A
Weight: .......................123 grams
Bracelet: .....................Steel, Oyster or Jubilee
Lug Width: ..................20mm
Watchwinder Direction: ..Both
From my personal collection, a 1997 T series GMT 16700:
Attachment 34666
One of the last of the tritium dials:
Attachment 34660
Lug holes case....a treat for the eyes:
Attachment 34659
There are no numbers here....this is one of the originals:
Attachment 34661
The GMT 16700 came equipped with the 28,800bph ca 3175 movement:
Attachment 33771
This movement features a full balance bridge for stability and accuracy, one of Rolex trademarks.. You can see the KIF shock spring at the balance pivot jewel:
Attachment 33772
A 24 hour hand that travels around the dial exactly one half the speed of the main hour hand:
The bezel is turned to the number of hours you are from local time to track any other time-zone in 24hr time, provided you have set your watch to local.
Here is an excerpt from the GMT 16700 Owners Manual:
Attachment 33991
Attachment 33992
Attachment 33993
Attachment 33994
While flying and controlling in Alaska I would set the bezel at -8 hrs to keep track of GMT time, a useful reference for pilots.
Attachment 34663
One unusual aspect of the 16700 - It was offered with the 93150 Sub Style bracelet (perhaps to fit over a flight suit?), a popular option which I preferred at the time:
This one still has the original 93150/501B bracelet - V9, Sept 1996 clasp code...Purchased in early 1997:
Attachment 34664
This was the last of it's kind, almost ignored because of the new 16710 and only a few of them were made:
Attachment 34665