Rolex SD4000 & Explorer II (ref 216570)

Laser Etched Crown Laser Engraved Caseback

2014 was the year Rolex unveiled some surprises including the re-introduction of an old classic, the Rolex SeaDweller 4000.  Originally launched in 1967 as a watch developed for depths and conditions greater than the industry standard Rolex Submariner, the original Rolex SeaDweller 2000 possessed functions and design elements that made it different from the Submariner. Just as how Rolex collaborated with Pan American Airlines on the development of the Rolex GMT, Rolex collaborated with COMEX S.A. to design a professional diving watch for depths beyond recreational SCUBA levels.  Fast forward to 2008 and the Rolex SeaDweller was discontinued with the unveiling of the Rolex DeepSea SeaDweller (DSSD), Rolex deep-water professional diving watch.

Time travel again to 2014 and Rolex's re-introduction of the Rolex SD4000 brings a dive watch that can be worn everyday (unlike the DSSD) yet has features setting it apart from the Submariner including the classic lines and design ethos that the first 1967 SeaDweller 2000 possessed. Incorporating Rolex's latest advancements, the SD4000 utilizes a Cerachrom ceramic bezel insert on ceramic bearings, Chromalight luminescence, Parachrom balance spring, and an updated Glidelock bracelet extension system.

Looking at the SD4000 and Rolex's other renaissance watch, the Explorer II 216570 illustrates the similarities and differences between them that make these both great everyday wearer sport / professional wristwatches.

Click any image for a larger picture

Rolex SD4000

Rolex Explorer II 216570

The Rolex SD4000 (left) and Rolex Explorer II (right) are both made of 904L stainless steel exclusively. There are no platinum or gold counterparts to these watches and are positioned in the Rolex line as bona-fide tool watches. The SD4000 ref 116600 and Explorer II ref 216570 keep the classic lines as their older brothers without the boxy re-design found on the updated Submariners and GMTs.

Both made of 904L stainless steel, the SD4000 and Explorer II proportions match their intended use. The larger Explorer II is designed for both daytime and nightime visibility with its 42mm face, larger indicies, and larger hands that hold more Chromalight luminova for longer lasting glowing at night.

The SD4000 is designed for water pressure and subsequently has a smaller, more compact traditional 40mm watch face, traditional 20 mm lug width (1mm narrower than the Exp II), thicker Triplock crown, thicker caseback, and thicker crystal.

Although very similar in weight, the proportions make the watches wear different. The Explorer II lies flatter on the wrist, and the SD4000 thicker caseback and crystal make it ride higher, even though it appears like a smaller, more compact watch.

Expl II 216570 SD4000 GMT II 116710
Endlink Width 21mm 20mm 20mm
Lug - Lug Length 50.1mm 46.25mm 48 mm
Height 12.5mm 15mm 12mm
Watch Face Diameter 42mm 40mm 40mm
Width inc/crown 45mm 44.5mm 44.3mm
Weight w/o bracelet 84g 93g 75g
Weight w/ bracelet (minus two Oyster links) 155g 165g 140g

Weight measured on an inexpensive electronic scale

Although very similar in weight, the proportions make the watches wear differently. The Explorer II (right) lies flatter on the wrist and the SD4000's (left) thicker caseback and crystal make it ride higher, even though it appears like a smaller watch. The lug-to-lug length is longer on the Explorer II giving the watch more wrist stability and daytime visibility.
Rolex SD4000 & Rolex Explorer II Rolex SD4000 & Explorer II Crowns
The vertical profile of the SD4000 sits higher than the Explorer II (left), yet the crown guards are very similar in proportion (right). The Explorer II utilizes the largest sized Twinlock winding crown rated to 100M (300 ft) which is the same crown found on the Rolex Milgauss; -no more tiny Twinloc crowns to futz with found on the older Explorer and GMT models. The SD4000 utilizes Rolex's Triplock winding crown rated to 4000ft (1300M). Both crowns are similar in diameter, but thicker SD4000 crown is somewhat easier to grasp.

Rolex SD4000 & Rolex Explorer II

The 2mm difference in watch face diameters make a discernable difference when reading the watch, yet one watch is not any less easier to read than the other. From this view, the Explorer II cyclops does make the date easier to read, but when read at an angle, the SD4000 wins. A SD4000 with a cyclops lens affixed would make the crystal uber-tall. Despite the prevailing thinking that because of the SD4000's thicker crystal, a cyclops lens would not work because of the optics involved. Despite this prevailing wisdon, others have shown a cyclops glued to a 3mm thick SeaDweller crystal works just fine.

The Cerachrom ceramic bezel found on the SD4000 is easy to read and the bezel rotates as smoothly as the ceramic Submariner and DSSD bezels, and much easier than the original, non-ceramic SeaDweller 16600 bezels.

I did notice that the SD4000 bezel is very easy to grip as the serrations are deep and extend around the edge of the bezel. I also noticed that the bezel *might* extend a tad more off the edge of the case than the DSSD bezel as it is very easy to grip and turn the bezel, or for a long sleeve shirt sleeve to turn the bezel without noticing it.

Rolex SD4000 & Rolex Explorer II

The difference in proportions continue with the different casebacks and how they sit on the wrist. The SD4000 (left) caseback is slightly smaller in diameter than the Explorer II (right), but the actual portion that touches the wrist is much smaller on the SD4000 because of the room required for the SeaDweller caseback engraving, and the thicker caseback adds increased height.

The 1mm wider lugs on the Explorer II are noticeable. The image on the right depicts the narrower 20mm SD 4000 bracelet slid into the Explorer II's 21mm lugs. That extra one (1) millimeter makes a difference. Rolex SD4000 & Rolex Explorer II
Rolex SD4000 & Rolex Explorer II
Can you tell which bracelet is which? A discerning eye might catch the greater taper in the middle links from the wider 21mm endlink down to the bracelet clasp. The SD4000 bracelet is on the bottom of the photo showing a more subtle taper from the 20mm endlink to bracelet clasp. The Explorer II bracelet is fitted with a non-standard Glidelock clasp found on the SD4000's and Submariners.

Rolex SD4000 & Rolex Explorer II

Rolex SD4000 & Rolex Explorer II
Making the SD4000 thicker than the Explorer II is the 3.2mm crystal. The Explorer II utilzes a 2.0mm crystal, but a thicker crystal is required for a deeper depth rating on the SD4000. Both crystals ride above the bezel line allowing more light onto the watch face. Crystals that are flush to the bezel such as on the ceramic GMT's do not allow for as much light as do raised crystals. Although probably not an intended feature, I have noticed that crystals flush with the bezel allow less light than raised crystals. The crystal edges on both watches are slightly beveled to prevent errant chips.
The SD4000 end link is raised slightly, similar to the DeepSea SeaDweller and original Rolex watches. The raised lug allows for better fitting over long wetsuit sleeves. I wish the Explorer II had this feature. Rolex SD4000 & Rolex Explorer II
Rolex SD4000 & Rolex Explorer II

How it Wears


SDc4000 to Work



After wearing the Deep Sea SeaDweller (DSSD), a 17mm high, 44mm wide, 215g behemoth of a dive watch for almost a year, the SD4000 is a sigh of relief. I have a 6 5/8th wrist and the DSSD was a great weekend watch, but my wrist started to feel beat after a few weeks of wearing it. When my wrist felt beat, I would switch to the Explorer II 216570 letting out a sigh of relief. To let my normal watch wrist recover, I would wear the Explorer II on the opposite wrist for a few days.

The DSSD is a fantastic piece of engineering and I would still be wearing it if the watch was not so top heavy and tall. I believe the DSSD would be more comfortable if it were less tall. I had to keep the DSSD pretty tight on the wrist. The much heavier platinum Daytona rides closer to the wrist and thus does not flop around as much.

The SD4000 is a great combination of rugged watch with thicker everything, yet has the relative comfort of the Explorer II. The traditional proportions from the 1967 SeaDweller on a 40mm case keeps the watch compact. I appreciate the thicker caseback raising the watch case higher allowing clearance between the crown and the back of my hand. A 150g watch is much easier on the wrist. If you like to have your watches slide around a bit like with the older hollow-link, tuna-can bracelets found on the originals, both the SD4000 and Explorer II allow for that without beating up the back of your hand. The SD4000's raised caseback and the slightly raised Explorer II caseback matched with the narrower Twinloc crown allow for both watches to be worn slighly loose

The SD4000 watch face is as visible as the Explorer II, but the hands are not. I appreciate the Explorer II's larger hands and as a result, slightly brighter lume because of the increased mass for extra Cerachrom lume. Additionally, the SD 4000 does not have the orange 24 hour hand, larger indicies, and other orange accents that I appreciate on the Explorer II. Ones who might be leaning towards the Explorer II because of the 24 hour hand and tracking a second timezone might be comforted that there are methods (listed here) for 12 hour watches with a rotating bezel to track a second timezone.

On the comfort side, both the SD4000 and Explorer II offer similar wearing experiences. The SD4000 is feels heavier and slightly taller causing a *little* more watch flop, but not anything like the DSSD. The SD4000 looks smaller on the wrist as the Explorer II, but has the same amount of watch presence. For ones who are desk diving or desk exploring, both watches are a coin flip. The Glidelock clasp standard on the SD4000 might sway me to the SD4000, but that feature is counteracted by the larger hands and dial orange accents, and 24-hour hand resident on the Explorer II. The smaller looking SD4000 possesses some very angular features (raised crystal, raised bracelet end links) that make the SD4000 stand out from the GMTs and Submariners. Between the two watches, I would have a hard time selecting just one. Both the SD4000 and Explorer II have features that I use daily. Too bad Rolex does not make a SD4000 Explorer merging all distinguishing features of both watches into one watch. Now there's an idea...

Rolex Crown
This photo and the one above of the SD4000 was taken on my drive to work. The sun hit the crystal at the correct angle and the etched Rolex crown became very apparent. These photos were taken with iOS app Hydra on an iPhone 6+. Hydra takes 50 to 60 images per shot, then combines them together for incredibly hi-res photos. In the top photo, you can see the second hand blur as the shot requires about 15 seconds to shoot.

Red Date Disk

It seems that every Rolex that has some color in it increases its value, as well as just looking cool. The Explorer II 216570 has an orange 24-hour hand, and the red Submariners are grail watches to many collectors. I was able to source an all red genuine, still in Rolex parts package date disk for the 3135 movement in my Rolex 116600 which is a spare part for most likely for the 2002 Turn-O-Graph 116264 that possessed an all red date disk.

The concept is not new. Early Rolex DateJusts had a red date wheel, as did the Turn-O-Graphs

DateJust Rolex Turn-O-Graph

Below are some images of the transformation with the help of my local Rolex certified/CW21 watchmaker. These photos were taken with iOS app Hydra on an iPhone 6+. Hydra takes 50 to 60 images per shot, then combines them together for incredibly hi-res photos.

Rolex SeaDweller 4000 Red Date Disk
Removing the caseback
Rolex SeaDweller 4000 Red Date Disk
Caseback removed. Thick gasket and full balance bridge with the balance wheel running on this Rolex 3135 movement . Click for the high res image. You can see the serial number of the main place which is different from the serial number located on the rehaut of the watch. Despite the different serial numbers, when a Rolex Service Center takes in a watch, they verify the authenticity of the watch by matching the case/rehaut serial number located under the crystal at the 6:00 o'clock with the main plate number.
Red Date Wheel
SeaDweller 4000 case with movement removed
Red Date Wheel
Ahh, the movement with original date wheel. Apparently there is a weak spot in the dial which my watchmaker had to reference in a book only available to certified Rolex watchmakers. Subsequently, he had to remove the dial very gingerly. There is a thin spot in the dial that will cause an indentation if the dial is removed by a gorilla.
Red Date Wheel
Here's the dial side of the SD4000 - 116600 with both the original black and red date disks.
Red Date Wheel
Red date disk installed. Notice the blued screws holding the date mechanism plate to the main plate of the Rolex 3135 movement. Even with blued screws, this is not your grandpa's watch.
Red Date Wheel
With the face reinstalled. The red contrast is perfect!!! -subtle but distinctive.
Red Date Wheel
Here's a better look
Red Date Wheel
With the hands installed.
Red Date Wheel

Here it is in the wild. I tried to capture the laser etched crown in the crystal but did not quite catch it. The slight touch of red makes the Rolex 116600 SD4000 perfect. The blur in the image is the second traveling while the image is captured.

A few more recent picts are below taken on my drive to the office.

Rolex Red Date
Rolex Red Date
Rolex Red Date

Rolex Caseback - Minus4Plus6
I wanted to make the SD4000 even more special. After I had the Minus4Plus6 logo updated in 2015, I thought that the logo on the caseback would do the trick. One of my long time pals owns CrashTag, a laser engraved identification tag for active outdoors people. My pal indicated that CrashTag utilizes LaserMarks as their primary engraver. I contacted LaserMarks and sent them a couple of generic casebacks to engrave. Once Mark at LaserMarks was able to fine tune the logo, and the depth, on the generic casebacks, he engraved the SD4000 caseback. I had the caseback reinstalled and pressure tested by my Rolex Certified watchmaker. The laser engraving is not very deep and could be easily removed with a satin bar. Also, laser engraving is incredibly precise with no rounded edges and corners.