Installing a Sapphire Caseback

Viewing the micromechanics inside your watch

16710 GMT 116710 GMT-C Preik New
Rolex Sapphire Caseback

For years, I wrestled with the decision to install a clear caseback on my 16710. I had seen pictures of other clear casebacks on Rolexes     and wanted to see the movement run. I decided to take the plunge and go with a sapphire caseback. I ordered a clear sapphire caseback from Thomas Preik  at Custom Watch Concepts a little more than a year ago, but chickened out on having the caseback installed and subsequently sold it. Despite selling the first caseback, I still contemplated a sapphire caseback and ordered another caseback and dove headfirst into this project. With no Rolex watchmaker storefronts in my county, I decided to take on the installation myself.

Click on any image for a larger image in a new window.

Sapphire Caseback

After completing two TimeZone online coursesand after reading how relatively simple the procedure is from other posts, I decided to take on this endeavour. The TimeZone courses gave me confidence in that I can open watch cases without breaking the watch. I have restored a few manual-wind watches since the TimeZone courses. If for some reason I made a mistake on my 16710T, or if I needed to send the watch to a Rolex Service Center (RSC), I know that I could always install the original caseback. Before this project, I did some research by emailing others who have opened up Rolexes, and, who readily gave me pointers on the supplies this procedure would require. Most of the tools I already owned from the TimeZone courses, with the exception of the caseback removing tool.
Champthekid emailed me this image of his sapphire caseback 3186 Rolex.

Tools Required:

Some Rodico putty for fishing out any dust/dirt/smudges that might fall into the movement.

  1. Caseback removal tool (more on this below)

  2. Casevise

  3. Jaxa wrench or caseback wrench for installing the new caseback. (I used a $15.00 eBay version)

  4. Replacement caseback gasket (Rolex part number: 29-332-10 for the GMT/Sub).

  5. Couple sticks of Pegwood

  6. Silicon grease

  7. Finger cots (optional)


Rolex Watch Tools

All of these tools are available from the usual watch supply houses (Otto Frei, Jules Borel, etc). Tell the supply house the case number of your Rolex and they will supply the correct gasket. For a 16710T, the gasket is Rolex part #29-322-10.

There are a couple of thoughts on the removal tool that I have either heard from others, or have seen. There are four caseback removal tools that are available each with advantages or disadvantages:


  1. Bergeon Butterfly Wrench: Modeled after the original Rolex caseback removal tool, this wrench is readily available. Use with a casevise, this tool slips on the caseback and using downward pressure, unscrews the caseback.

    Advantage: A no nonsense tool.

    Disadvantages: Without the proper amount of downward pressure, the tool can slip causing scratches and rounding the teeth on the caseback. I had seen one watchmaker remove a caseback without any casevise using both this hands; watch in one hand and butterfly wrench in the other. He obviously knew how much pressure to use, plus he has sports a Tony Sopprano figure and upper body strength.

  1. Bergeon or Horotech Press: This tool costs approx $500 and from what I understand, is a great tool from removing Rolex casebacks, but for a hobbyist this tool is overkill.

  1. Cheesy EBay caseback removal wrenches that indicate Rolex: These wrenches use three pins that are really good for installing the new caseback, but not for removing Rolex casebacks. Avoid these.

  1. LG OpenAll Caseback remover: I selected this one as it appears to prevent the caseback removal die from slipping and is relatively affordable. The only word of caution is that this tool works against itself. The more downward pressure you apply by screwing the press, is the amount of pressure the caseback pushes against when being removed. Be cognizant that one must unscrew the press while unscrewing the caseback or else the case threads might strip.


This tool has an option of being placed into a bench vise, or for $15 extra, comes with a base that is bolted into a bench. (Bonus points to anyone who recognizes the Concor sticker and the year; its an indication how long I have had this table). I found myself not using that base at all so it is not needed.


The Steps:

1. Remove the bracelet: There are plenty of tutorials on removing a SEL Rolex bracelet. In these pictures, I have a two piece Martac band installed that can easily be moved out of the way. I use the Martac band while wearing the watch road cycling. One method for removing the bracelet is here.

Rolex Watch Caseback
Rolex Watch Casevise


Rolex Watch Caseback removal tool

2. Place the watch head in the casevise. Pay special attention to where the cyclops is situated. Turn the watch head so that the cyclops does not rest against the casevise.

3. Select the correct size caseback die and install it into the caseback removal press (or butterfly wrench). Place the casevise into the LG caseback removal tool. Place the caseback removal press into the base, or into a vise.

4. Line up the watch head, the casevise, the removal die while the case vice and removal tool clamp holding the case vice are still loose. Be sure that everything lines up (eg. die squarly on the caseback, watch case squarly on the case clamp, and case clamp squarly on the caseback removal tool and tighten all the various clamps.

5. Turn the blue knob so that there is a fair amount of downward pressure. Insert the bar into the removal press.

Gently unscrew the caseback, watching that there is enough pressure that the die does not slip, while insuring that the caseback is not being screwed into the press too tightly. Once the caseback breaks free, I slowly turn the blue press knob counter-clockwise while moving the breaking bar counter-clockwise so as to not strip the case threads.

Once the caseback is fully broken loose, unscrew it by hand but, keep the caseback on the watch until you can get to a clean area to rest the watch.


Rolex Watch Movement 6. Once in a clean area, rest the watch facedown on a clean surface and remove the caseback. In this image, you can see the tell-tale signs of a Rolex movement. The brown arrow shows the movement holding screw, the red arrow shows the rotor lockring, the blue arrow illustrates the balance bridge, and the green arrow shows the Rolex mainplate number.


Cleaning Rolex Watch Movement
7. Remove the gasket and inspect the area around the groove where the gasket rests. Dab (do not rub sideways) Rodico to remove any dirt, smudges, and gunk such as the dried silicone grease shown in the left picture. Be sure to rotate the rotor over the balance using peg wood or a finger cot to prevent any dirt from falling into it.


Rolex Watch Caseback Installation 8. Apply silicon grease onto the new gasket using a gasket sponge and reseat into the groove where the gasket rests. Use the peg wood to keep the slightly stretched gasket in place.

9. Carefully rest the new caseback into the case level with the case and slowly screw the sapphire caseback using your fingers. Be sure to monitor the gasket insuring that it does not slip out of place.

Rolex Watch caseback tool

10. Once the caseback is past the point of being finger tight, use the Jaxa wrench to tighten the sapphire caseback onto the case as tight as possible, just leaving a smudge more room to tighten. Gaskets and O-rings do need some room to breath.


The new Preik casebacks use the same 29.5mm caseback tool as the Rolex caseback. Installation of the new caseback is the same as the removal steps but in reverse. See below.


Once installed, look at the caseback and the case using a 4x loupe to make sure there are no gaps.

Viola, the process is pretty straight forward and found it similar to replacing the oil and filter in one’s automobile. I found that installing a SEL bracelet without scratching the case requires more finesse than this job. Information on replacing an SEL bracelet can be foundhere.



Rolex Watch Casebacks

After purchasing the 16710, I had the watch pressure tested at the Beverly Hills RSC. Upon inspecting the original caseback, one can see the watchmakers inscriptions indicating when and where the watch was opened.

The inscription reads as follows:RBH 5/07 3/008 7380

The RBH (Rolex Beverly Hills) makes sense, as does the 5/07 (date). The other numbers are Greek to me.

Watchmakers inscriptions on the caseback is a long held tradition in the world of watchmaking that Rolex follows.

Thoughts on the sapphire caseback:

With the new caseback, I find myself looking at the back of the watch at any moment I get. I now reference the Rolex parts books and exploded views of the 3185 movement identifying parts. Folks have mentioned that a clear caseback is a tell-tale indication of a fake Rolex. Nonetheless, a Rolex connoisseur will recognize the ring used to hold the rotor in place, the Teflon coated reversing wheels, the free-sprung balance and balance bridge (vs. balance cock used on most other watches), the set screws used to hold the balance into the case, the reference number on the main-place, as well as many other distinctly Rolex details.

The sapphire caseback is rated at 200M/20ATM, it is slightly higher rated as the original caseback and less than the Sub/SD caseback at 300M. The machine quality of the sapphire caseback combined with the integrity of the Rolex case design makes me confident that the new caseback and the seal will repel water pressure as the original caseback.

The watch wears the same but rides a little higher. The original caseback made the watch ride at 12mm thick and the sapphire caseback makes the watch ride at 12.47mm. With the increased thickness of the sapphire caseback, the watch is a little higher, but not to the degree of a Submariner or a SeaDweller.

Update: In Antiquorum's Rolex Revolution Catalog, page 158 lists a Rolex transparent caseback for a GMT Ref. 1675. Click on the images for the larger pictures. It is comforting to know that even in 1962, Rolex wearers requested transparent casebacks for the same reason why I installed the one from Thomas Preik.

Ref 1675 Transparent Ref 1675 transparent story


Update: Since writing this page, I have since sold this particular 16710 in favor for the M series 16710 with a 3186 movement (below).

Rolex 16710A

I have worn this watch for a few week and have realized that the sapphire caseback has two distinct advantages:

  1. The watch rides slightly higher which prevents the crown from digging into the wrist when worn loose.

  2. It is hard to scratch the caseback when the watch is at rest on the nightstand as sapphire is much harder to scratch than the traditional 904L stainless caseback.

After installing the caseback, I asked a watchmaker to pressure test the watch which tested fine at 100M/10ATM.

This was a worthwhile project that anyone with a steady hand and controlled environment can do.

Rolex BigSur
Big Sur, Central California coastline

Click on any image for a larger image in a new window.

Sapphire Caseback for GMT-C 116710

I learned of sapphire casebacks for the newer Rolex cases such as the GMT-C on The Rolex Forums.

Swiss Watch Customs manufacture a sapphire caseback that is different from the Thomas Preik caseback Swiss Watch Customs casebackis designed closer to the original Rolex caseback and subsequently, fits into a Rolex GMT-C. The caseback is made of 316L steel, has a Hitrel gasket between the crystal and the caseback, and has the same bubble-back profile that the original Rolex caseback has with the serrations for a Rolex caseback socket.

Sapphire Caseback
The Swiss Watch Customs caseback has the same profile, bevel, and serrations as the original caseback. The Swiss Watch Customs caseback appears similar to the specially made sapphire caseback sold at the Rolex Antiquorum auction. Ref 1675 Transparent

What is appealing of the Swiss Watch Customs caseback is that it attempts to mimick the original Rolex caseback, whereas the Preik caseback does not


Stainless Sapphire Casebacks
Rolex casebacks have approximately a .5mm 90 degree edge on the caseback. Pictured left is the 16710 caseback and the one pictured on the right is the GMT-C (116710) caseback. The Preik caseback does not have a 90 degree side edge, whereas the Swiss Watch Customs caseback does have a 90 degree blocked edge similar to the original Rolex caseback.


The casebacks are of slightly different thicknesses.

The sapphire caseback does add a slight amount of height to the watch, but it is not noticeable.



  • Swiss Custom: 4.54mm
  • Thomas Preik: 4.78mm
  • Rolex GMT-C 116710 / 2350: 4.46mm
  • Rolex GMT 16710 / 2180: 4.67mm

Even though the 16710 (GMT-T) and the 116710 (GMT-C) casebacks look very similar, they have two different part numbers engraved on the inside of the caseback.

The 16710 (GMT-T) is part number 2180, and the 116710 (GMT-C) is 2350.

GMT Casebacks
GMT-C Caseback GMT-C Caseback
Unlike the traditional GMT and Submariners, the backs on the new cases are recessed into the watch case. Subsequently, the Preik caseback would leave an open seem in the caseback. The Preik caseback would fit on the GMT-C, but the open seem would be susceptible to catching grit, grime, and such. The case was designed for the caseback edge to fit flush with the case.
Caseback Series 116710 Casebacks
The 16710/GMT-T casebacks (left), and the 116710 GMT-C casebacks (right). The Swiss Watch Customs caseback (right) is very similar to the original caseback (left), including the bubble back quality that is not in the Preik caseback which has an entirely flat crystal.
With the GMT-C caseback removed, the same steps listed above apply. The gasket must be removed, and the dried silicon grease and gunk needs to be carefully wiped out using Rodico. Caseback Removed
With the gasket removed, and the gunk cleaned, replace with the new sapphire caseback. Be sure to have silicon grease on the gasket, and some grease on the caseback threads. Clean
Ball Installation

Swiss Watch Customs utilizes a rubber ball, or nylon press tighten down the caseback.

Unfortunately, each time I used the ball, I was able to still move the caseback with my fingers. I eventually resorted to using the caseback press (shown above) to fully torque down the caseback. Fortunately, the serrations are approximately 29.5mm in diameter so the same Rolex caseback socket fits, but it is not a precision fit like with the originalsRolex caseback. The press kept the caseback socket from slipping; a hand wrench with the serrated socket might not work as well.

After using the press, I felt confident that the caseback is installed correctly.

The finish of the Swiss Watch Customs caseback is very similar to the Rolex case finish and it is obvious that this brand caseback is made for Rolex.

Now with a 316L, 10ATM sapphire caseback, I can now marvel at the micromechanics inside the watch, as well as watch the ParachromBlu hairspring do what it does best.

Update: After wearing this caseback for a few months, I have noticed that the Swiss Watch Customs caseback lets in more light thus making viewing easier on the eyes, but there are more reflections off the crystal because of the beveled edge. After using both styles of casebacks, I prefer the flat crystal on the Preik caseback.

Sapphire Caseback


Thomas Preik Updated Sapphire Casebacks

Thomas Preik updated his sapphire caseback such that it installs wiht a standard 29.5 Rolex caseback wrench.

The new caseback has a finish that matches closely to Rolex's 904L steel. Unlike the Swiss Watch Custom caseback and ball, the Preik caseback installs well with a standard 29.5 Rolex caseback tool.

Preik New
The Preik caseback is advertised to work on both the 116710-C and the 16710-T models. I first tried the caseback on the 116710-C. 116710-C caseback

This is a side-by-side image with the original 116710-C caseback on the left, and the new Preik caseback on the right.

Notice that the original caseback has a 1mm edge whereas the Preik caseback is tapered.


Side by Side

The caseback installed well and easier than the Swiss Watch Customs caseback because a Rolex tool fits the caseback snugly. Unfortunately the Preil caseback has a tapered edge that sits deep into the recessed GMT-C 116710 case.

Although the caseback fits snugly and I am confident that it is waterproof, the recessed edge might be a place for dirt and grime to collect. Nonetheless, the caseback does fit snugly and should function normally as the original caseback.

116710-C seam
After installing the caseback on the GMT-C, I installed the Preik caseback on a GMT 16710T and the caseback sits on top of the Rolex case just like the original caseback. 116710-T
Height Difference

The standard caseback is on the left, and the Preik caseback on the right.

The Preik caseback does ride a little higher than the original casebacks.

  • Rolex GMT-C 116710 - Orig: 12.28mm
  • Rolex GMT-C 116710 - Preik: 12.63mm
  • Rolex GMT-T 16710 - Orig: 12.1mm
  • Rolex GMT-T 16710 - Preik: 12.4mm

Thomas Preik definately improved his caseback by incorporating the Rolex style caseback wrench for installation. Unlike the Swiss Watch Customs caseback that has a beveled cross section to mimick that standard Rolex caseback, the flat crystal design Preik's caseback is very clean and clear with no reflections that distract from viewing the watch's inner-workings.

I hope Preik manufactures a caseback that will install flush with the newer recessed Rolex watch cases found on the GMT-C 116710. Although the caseback functionally works on the newer cases, I hope slight redesign for the newer cases will make a closer cosmetic match with the watch.