Movement

The movement has been reexamined and the Rolex GMT-C 116710 movement has redesigned elements that set it apart from the original 16710s. The movement inside the traditional 16710T ("T" for no-holes pierced case) movement is a time-tested 3185 movement that allows for moving the hour hand independently forward/backwards as the user travels through time zones. The 116710's 3186 movement includes the Rolex's proprietary Parachrom Blu hairspring, and according to James Dowling in a TimeZone post, the wheels of the drive train are closer together removing some of the gear play felt in the 16710 when the hour hand was being set. Anyone new to Rolex would not notice, but when compared side-by-side, there is a little more slop when setting the hands of the 16710 than there is with the 116710. Update:The 3186 movement and Parachrom Blu hairspring are installed in late Z and all M-series 16710's and M-series Explorer II's. More information is posted here. A video of the making of Parachrom Blu is posted here

 

The Case

The 116710 case is larger, thicker, and 1.5mm longer than the 16710T case. The increased size and weight give the watch a much heavier feel than the traditional GMT. Although the watch case is thicker, similar to a SeaDweller in thickness, the watch rides closer to the wrist because the caseback is flat (top picture) and does not bubble like the 16710T (bottom picture). Subsequently, the watch rides much closer to the wrist thereby negating any watch-flop and top heaviness

Weight

All of the redesigns incorporated in the 116710 have made the watch heavier than the traditional GMT. My 116710 weighs in at 141g on my kitchen scale. The traditional GMT comes in at 116g. Both of my watches have two links removed so that they fit on a 6.5-6.75" wrist.

As a comparison, the chart posted here, lists the Submariner at 135g and the SeaDweller at 147 which is in the same range as the 116710. It appears that my kitchen scale might be weight light as the same chart shows the 16710 127g, ten grams heavier than what my scale indicated.

Height

The height of the 116710 is reported as being 13mm, but many measure it as 12mm. The 13mm height is similar to a Submariner and 1mm taller than the 16710T. The extra millimeter is hardly noticeable; the weight difference is more noticeable than the height difference.

 

Crystal, Cyclops, & 24 Hour Hand

Both watches have a flawless sapphire crystal. The cyclops on all Rolex models are glued to the sapphire crystal and folks removing the cyclops is well documented on the watch boards.

Differentiating the models is the anti-reflective coating under the cyclops of the 116710. The picture on the right attempts to show the difference between the two models' cyclops and how they reflect light. I have found the cyclops on the 116710 much easier to read and has less glare.

First time Rolex wearers would not notice the difference, but there is a noticeable difference when viewing the date between the 16710T and the 116710. Viewing the date is easier on the 116710 and one does not have to look at the cyclops straight-on as with other Rolex models.

 

	Update: Jon on TimeZone learned that the antireflective coating is on the underside of the crystal. There are various methods for removing the cyclops as it is glued onto the main crystal. Some rolex wearers soak the crystal in acetone, and others have knocked it off using a razor blade. According to the Tech Spec Sheet below, there is anti-reflective coating on both sides of the main crystal.

The green 24 hour hand on the 116710 is also a noticeable difference from the red 24 hour hand on the older model. Any Rolex model with the Rolex Green signifies that the watch model is over 50 years old, such as the green bezeled LV Submariner, or green crystalled Milgauss.

The 116710 also had the Rolex branded rehaut with the Rolex-Rolex-Rolex engraved as well as the watch's serial number engraved at the 6:00 position. The Rolex branded rehaut is referred to as the RBR or "Rolex Branded Rehaut." The rehaut is commonly mistaken for the chapter ring, but this is incorrect.

The Crown

Another significant difference between the 16710T and the 116710 is the use of a time-tested Triplock crown. One of the frequent criticisms of the 16710T was the Twinlock crown that is perceived as being too small and did not match the design of the case. The Twinlock crown does not fit flush onto the case as it does with the DateJusts. Historically, the Twinlock crown has always been part of the GMT as this watch evolved the DateJust and the early Turn-O-Graph.

The design difference between the two crowns, and the significance, is both the size and the number of o-rings used to prevent water penetration. The smaller Twinlock crown has an o-ring in the crown, and one in the tube. The Triplock crown uses four o-rings; one outside the tube that is visible when the crown is unscrewed, one in the crown, and two in the tube.

Even with the Triplock crown, the 116710 is still rated as being water-resistant to 100M and not 300M as with the Submariner. The design difference between the Sub and the 116710 is the caseback. Even though the 116710 has the same crown and heavier case as the Sub, the caseback is of similar thickness as the GMT-DateJust series. As in a picture shown here, the caseback flexes under pressure and thereby keeps the 116710 rating at 100M (although your mileage might vary…).

 

The Bracelet

The 116710 bracelet uses solid links rather than hollow links as the traditional Rolex models. The updated bracelet fits similar to the new TOGs and DateJusts. The links on the 116710 are not as thick as the 16710T near the watch head. The difference is slightly noticeable to the eye, but not to the wear and feel of the watch.

Just like the newer TOGs and Datejusts, the redesigned bracelet has a built-in expansion link that appears to adjust the bracelet the same as moving the bracelet in the adjustment notches inside the clasp. The expansion link is a welcomed feature, especially when adjusting the bracelet is a little harder on the 116710 than the traditional Rolex clasps as there are no holes. I have used ballpoint pens, tooth picks, thumbtacks to make quick bracelet adjustments on the 16710.

The Clasp

The clasp on the 116710 is thoroughly redesigned and is a design marvel in itself. This new type of clasp is not used on any other Rolex, except the Yachtmaster II. The clasp is milled stainless and is similar in construction as the newer clasps used on the TOGs and DateJusts. Setting this clasp apart is the spring loaded hook inside the clasp. A spring keeps the clasp hook locked in place, and a springbar keeps the security cover locked in place. The security cover on the 116710 does not use compression to keep the buckle closed as in the 16710T, but rather it keeps the tab from moving backwards. The security cover moves freely when opening and closing with no friction on the side of the clasp cover, as with the 16710T.

 

The clasp schematic from what Hannes found in the Rolex patent design illustrates how complex the new clasp is, but the schematic does not show the hook noted by the blue arrow in the photo above.

There is more insight on how this clasp functions in the Rolex US Patent document posted here (right click and save the .pdf to your desktop).

 

Inside the clasp are three notches used for micro-adjustments that are spaced the same as other Rolex clasps. Most Rolex clasps have four-five micro-adjust holes in the clasp, but the 116710 only has three. The expansion link under the clasp can act as a fourth level of adjustment. More information on the micro-adjust holes on Rolex bracelets can be found here.

 

 

 

 

 

 

 

One significant difference between the traditional "tuna-can" style clasps and the milled clasps found on the new GMTs, Milgauss, TOGs, and the redesigned Submariner and DeepSea is that rather than the clasp being riveted to an oyster link, it is held by a screw. The advantage with a screwed clasp is that for smaller wrists, it is easy to have four links on the 6:00 o'clock side rather than minimum five links on the traditional bracelet. The GMT-C band on the left has four links, whereas the traditional GMT band on the right has the minimum five links.

More information on bracelet fitting can be found here

Maxi Dial & Hands

The introduction of the LunetteVerde (LV) Submariner and 50th Anniversary Submariner, as well as the YachtMaster 16622 showed a redesigned watch face with larger hands, and larger indices. This same type of dial and hands is on the 116710, but with a larger hour hand and hour markers than its maxi-dialed predecessors. The readability is improved, but there were never really any problems with the readability of the 16710T watch face. The maxi dial and hands do assist with the nighttime luminescence of the watch. These distinct qualities that are equally important and to decide between the two is hard. Like with all Rolexes, the hands and hour markers are made of white gold and inlaid with SuperLuminova. The mercedes hour hand is designed such that it can hold more SuperLuminova without the SuperLuminova cracking. My only criticism of reading the watchface at night is that it is hard to see the 24 hour hand. The arrow is the same size as an hour dot/indicator which makes the 24 hour triangle hard to discern at night. In both of this image of both watch faces, the 24-hour triangle disappears (hint: it's at 2:00 o'clock).

 

The Ceramic Bezel

One of the distinguishing features of the GMT is the 24 hour bezel used to measure various timezones. The bezel of the 16710 uses a click-spring to hold the bezel in place. Earlier GMTs (GMT Master) had no clickspring which allowed the bezel to slide in either direction. The 16710 (GMT Master II) uses a clickspring that prevented the bezel for being knocked from its setting, but the older spring allowed for the bezel to move easier counter clockwise than rotating clockwise.

The bezel on the 116710 is thoroughly redesigned. The bezel rotates on three ceramic ball bearings similar to the new TOG’s that rotate on steel bearings. Rolex has moved past the design concept of the bezel sliding by compression on a small washer. The 116710 bezel clicks in one-hours jumps and not in minutes as the 16710T. Each rotation the user feels a noticeable click of the ceramic bearing holding the bezel in its setting (Schematic from Watchtime Magazine, Rolex Special Edition). In Rolex's 2008 Basel media release on the DeepSea model, the ceramic bezels are referred to as CERACHROM. CERACHROM appears very similar to the ceramic bezel used on the 116710, but the numbers are flush on the bezel and not indented like they are on this model and the Ya.phpaster II bezel. According to James Dowling, either platinum (silver color) or gold (all gold and two-tone models) is used to signify the numbers on the bezel. The numbers are held onto the bezel using Physical Vapour Deposition (PVD) which allows the metals to be placed in the exact position in the exact thickness. Gold is used for the bezel numbers on the 18k and 2 tone ones because it matches the gold on the bezel and platinum is used for the steel one because steel cannot be deposited, but platinum works well.

 

 

Update: The TimeKeeper Forum had a thread regarding someone who actually removed a GMT-C bezel. These images show the simple construction, but dont show how difficult it is to accomplish, and how fragile the GMT-C bezel insert is. [Images on chipped GMT-C bezels are here.] Click images for larger pictures

There is more insight on how 116710 ceramic bezel works on the Rolex US Patent document posted here (right click and save the .pdf to your desktop).

Rolex also developed a two tone ceramic bezel. Look at the Rolex US Patent document posted here (right click and save the .pdf to your desktop). A January, 2008 US Patent document is posted here(right click and save the .pdf to your desktop).

Update: December 2016 In Rolex Magazine #6 released Fall 2016, I noticed that the Submariner bezels have a Bezel Insert Ring to support the ceramic insert (shown left)
Examining the US Patent Documents (above) it appears that the GMT ceramic bezel assembly does not have the supporting ring that the Submariner's, and by extension the DSSD and SD4000 possess in their assembly. Perhaps this is the reason why one sees more damaged GMT bezel inserts in the Extreme Rolex - Ouch page than any other model.

 

The bezel on the 116710 is noticeably much thicker than the traditional GMT in order to hold the ceramic insert in place. The bezel is almost as thick as a SeaDweller bezel. Its easy to grasp and rotate. Much has been said on the durability / fragility of the ceramic bezel insert. After a month of use, there are no scratches on the bezel insert nor has there been any chipping/cracking.

There is more insight on the composition of the new composite ceramic bezel inserts in the Rolex US Patent document posted here (right click and save the .pdf to your desktop).

 

When discussing GMT bezels, I have to digress on a relatively new discovery on Rolex's change in clicksprings. I discovered when ordering a replacement clickspring for my GMT (16710T), that the newer replacement springs are longer, allowing for the bezel to move clockwise/counter-clockwise easier. I looked at Z series 16710T's and Yachtmasters at an AD recently and noticed that they use the same new clickspring as the bezels moved easily clockwise as they did counter-clockwise. The new clickspring is much better than the older, original clicksprings that made the bezel rotate counter-clockwise easier, and harder when rotating clockwise. The new clickspring is the one pictured on the top, and the original on the bottom. Notice that the new clickspring, when installed, bows in the opposite direction than the original clickspring, as well as being much longer causing it not to bind like the original clickspring. The original clickspring allowed the bezel to rotate clickwise, and bind somewhat when the bezel was rotated counter clockwise.

The Rolex part number I ordered through my watchmaker who has a Rolex parts account was 317-16628. This part number covers the following case numbers: 16268, 16622, 16628B, 16700, 16710, 16713, 16718, 16758, 16760. Don't allow your watchmaker to confuse the 16628 spring with part number 317-16800 clickspring as that one is designed for all the Submariner models (14060, 16600, 16610, 16800, etc).

A schematic of bezel inserts, bezel part numbers, and springbar part numbers is posted here (right click and save the .pdf to your desktop).

A Rolex created tutorial on how to use the 24 hour bezel is posted here (PC) and here (Mac).

Rate - Accuracy

Many have reported that the 116710 is dead-on with no deviation. My 116710 is about 1 second slow each day with no deviation from day-to-day. My 16710 is 2.5 seconds fast each day, also with little deviation from day-to-day.

Bling vs. Tool

Along with the GMT redesign came another aspect that is finding its way on all Rolex watches is the use of mirror finishing. The mirror finish "scheme" found on the newer DateJusts, TOG's, and Daytona's have found its way to the GMT. Many Rolex followers have shied- away from considering the new Rolexes because of the mirror finish used on the center-links of the bracelet and on the case. Traditional Rolexes have a brush finish that reflects less light and hides scratches which helped define it as a “tool watch.” Sub's, SeaDwellers, and GMT traditionally hid scratches well because they were designed with specific functions rather than as "jewelry." I too had the same concern of flashiness when considering a 116710 as this was one of the reasons why I flipped the TOG I owned a couple of years ago. The TOG had mirrored center links as well as a larger than normal, fluted white gold bezel. Both the bracelet and the bezel were a little too flashy for my tastes, although I was drawn to it by the red second hand and the updated bracelet clasp.

The new 116710 is somewhat flashier than the traditional GMT and Subs, but not as much as the TOG. The bezel is not as reflective as the TOG although I do find myself questioning whether the 116710 reflects/mirrors too much light. There has been discussion on many of the watch boards that the 116710 is considered "smart casual" in the same vein as the Daytona. The 116710 is definitely not as attention getting as the diamond covered versions, but its mirror finish might standout when wearing your camping or household chore clothes. The top right image is one supplied by 1680 on Timezone shows his 116710 with brushed links (click on images for larger pictures.) The top left image and the one on the immediate left are from cx007 on Timezone. In consolation though, I am not as hung-up on scratches as I was with the TOG and my traditional GMT. As the watch gets scratched, it creates its own brushed finish and its own patina. For one still concerned with bracelet care, I have a DIY page on bracelet and case maintenance posted here.

 

How it wears & final thoughts

	The 116710 is the best wearing Rolexes I have owned. The slightly longer watch case allows me to wear the watch a little tighter than my traditional GMT. My traditional GMT is either too tight or too loose. I rarely use the expansion link hidden in the 116710 clasp, but am glad to know its there for when it heats up outside or when I travel to more humid states. I appreciate the weight of the 116710 and the green GMT hand is visible and a nice touch reminding me the pedigree of the watch. In essence, the 116710 is a fantastic watch that will help define the Rolex look for years to come.
Update after three years.
After owning the GMT-C and GMT 16710T for more than three years, my thoughts are mixed on which watch I prefer. Although the GMT-C has technical innovations/revisions that are fitting and appreciated, the GMT-C just does not seem to have the same soul as the classic GMT. I wear my GMT-C during the week and the classic GMT on weekends. I appreciate the improved cyclops, the triplock crown and the increased lume on the GMT-C, but do not appreciate the polished center links (PCL) and had the bracelet brushed (see below), the larger ceramic bezel numbers, and the fear of breaking the
ceramic insert (although I too have tested its durability a few times over the last three years). I am also not sure how to clean the bezel on the GMT-C when grit gets in there whereas it is an easy job with the GMT 16710T. When I put on the classic GMT 16710T, I do feel that this watch has more history and soul. I appreciate the rattle of the hollow link bracelet, and the simple tuna-can clasp that can be quickly adjusted with a toothpick or ball point pen. I also fitted the watch with a faded black-red bezel insert. My traditional GMT does have the 3186 movement, but it is lost when I read the date that just does not have the clarity when compared with the GMT-C. Others have described the difference between the GMT-C and the GMT 16710T as being similar to owning/driving the watercooled Porsche 911 and the aircooled Porsche 911. The watercooled Porsche 911 is more technically advanced than its predicessor, the older aircooled 911 is much influential and inspirational and considered the classic enduring Porsche. I feel the same way between the GMT-C and the GMT 16710T; each one has it enduring qualities that sets them apart, but not necessarily above each other.

UPDATE: After 19 months, I had the polished center link removed.

After 19 months of owning the GMT-C, I decided to have the bracelet brushed. After seeing the DeepSeas and AirKings with a fully brushed oyster bracelet, I knew that the bracelet on my GMT-C should be brushed. Since taking ownership of the GMT-C, as well as when I owned a Turn-O-Graph, I was always somewhat schizophrenic on the polished center link. The Rolex mirror finish is par-excellence and there is a certain robustness that indicates that the reflection is there to last. Polished center links certainly work on the Ya.phpaster and Milgauss as the lugs are also polished, but the lugs of the 116710 are already brushed and a brushed bracelet seems to match the watch head much better. In this economy as well as in the government job that I hold, the flashiness did not fit on a number of levels. I could have brushed the bracelet myself using Bergeon satin bars, but Fourtane Estate Jewelers offered to do it for me. Fourtane's watchmaker did an excellent job. Although many have reported brushing the bracelet themselves using a 3M Scotchbrite pad, the bracelet and the overall effect comes out much better when professionally done. The watchmaker at Fourtane explained that the bracelet is first removed, then prepped which includes an ultrasonic cleaning. Once prepped, the watchmaker uses a high speed (over 1000 rpm) wheel using a series of Bergeon satin wheels. The trick to an even brush job is the amount of pressure applied on the bracelet while on the wheel as well as the direction that the links are pulled across the wheel. The watchmaker explained that it takes practice to get it right. The bracelet came out fantastic. Fortunately, the re-designed Submariners (116610) have fully brushed bracelets. A brushed bracelet matches the satin finish on the watch head, fits Rolex's pedigree and history, and frankly, I think Rolex got it wrong when they included polished center links in the specifications. Brushed links understates the appearance of the watch, but improves the stout sport appearance that is part of Rolex's provenance. Click photos for larger images
Notice that the solid end link matches the finish on the lugs.
Here is the bracelet profile. This is the mark of a professional finish where the grain is consistent across all the links, parallel throughout all the links with an even weight spanning the entire length of the bracelet.
Perhaps the greatest surprise is how well the clasp looks. A fully brushed clasp makes the watch look durable and rugged, without the flash. The watchmaker disassembled the clasp to fully brush each of the pieces, including the cover on the underside of the safety-clasp.
These images do not fully capture how the removal of polished center links adds to the rugged look and appeal of the 116710. If you are considering a 116710 yet mixed on the polished center links, just have them brushed by a competent watchmaker. After having the bracelet brushed, it feels like I have a new watch.
Update: Champ the Kid posted these images on TimeZone of his brushed GMT-C bracelet. Now these images do the watch and the effect justice. (Reposted with Permission)
Using a GMT or Standard Watch as a Compass
One of the neat features of the 24-hour hand found on GMT's is the 24-hour hand. When the 24-hour hand is set to local time, it points north when the 12 hour hand points to the sun (Northern Hemisphere).
This is another method for 24 hour hand-less watches, but the 24-hour hand is between the minute and 12-hour hand when the 24-hour hand is set to local time.
For the Southern Hemisphere, hold the watch overhead, or do the what the images above illustrate.
According to Rolex, the Rolex Explorer II can be used as a solar compass for orientation during expeditions at whatever time of the day, by simply pointing the hour hand towards the sun while holding the watch horizontally will result in the orange 24-hour hand indicating the north in the northern hemisphere, or the south in the southern hemisphere. The only requirement is that both the regular and the 24-hour display are set to the local time.
Tudor Chronometer Manual Yet another method for watches with a rotating 12-hour bezel