The Mauron Musy GMT Sport reference MU04-203 is a luxury watch that is 100% Swiss-made. We’d hate to burst anyone’s bubble, but there’s a good chance a scary-large portion of Swiss luxury watches couldn’t (and indeed don’t) make the same claim. This five-man team, armed with a solid engineering background and a discerning choice of Swiss suppliers, has been in the game for eight years, making slow but steady progress in fine-tuning their wares. Let’s see where they are at right now.

Cutting to the chase here, the Mauron Musy GMT Sport watch is priced between $12,900 and $13,900, which is ambitious not because it doesn’t have the hardware to support it (it does, and we’ll get to that soon), but because that’s big money for a small brand. But consider this: Some three decades into the renaissance of Swiss luxury watchmaking, it’s very likely there are more disillusioned or just flat-out bored luxury watch buyers out there than ever. Some of them had three decades of experiencing all the big names they cared about – whether or not the big names “cared back” in return is another considerable factor. And so a flurry of high-end small brands has been on the rise in recent years, confidently aiming at the high four-figure, low-tens of thousands market of watches. Their hopes? To offer something that would save saved bored watch lovers from making another misguided purchase at a duty-free shop the moment things open up.

Advertising Message

From our first review on the origins of Mauron Musy, established by two engineers, Eric Mauron and Christophe Musy: “The two met in the late 1990s when Eric was the managing director of Régis Mauron SA, a company that specialized in the machining of mechanical parts, and Christophe was serving an internship as a mechanic. It was more recently, in 2012, that they set out to create something new and that the Mauron Musy company in St. Aubin, Switzerland, was born. That ‘something new’ was to be based on their extensive knowledge and experience in precision engineering – a prowess you can actually sense and feel when you pick the Armure up…

About nO-Ring Technology & 300m WR

Check out that review to learn more about their own “nO-Ring technology” that allows Mauron Musy watches to do without O-ring gaskets completely. Long story short, the two-man team responsible for machining (Eric Mauron and Olivier Cantin) have taken their knowledge and experience in high-precision parts manufacturing and used it to craft case components that are so extremely precise in their fit and finish that it eliminates a need for gaskets.

Furthermore, the nO-Ring technology does away with clamping screws to avoid any risk of deforming the case components’ flat surfaces. Therefore, the front and the back are clamped down by satellite springs placed around the entire perimeter, compressed and tensed by the closure of the case-band, bezel, and hinges. In essence, the technology is based on the components’ surfaces being machined and fitting together with extremely high precision, held together by the controlled tension achieved by the springs and hinges.

Advertising Message

The crown pulled all the way out. Notice the lack of threads and O-ring gaskets.

How much do you see, feel, or experience from this when wearing the Mauron Musy GMT Sport? A notable plus over other 300m WR watches is that although there is no screw-down crown on the GMT Sport, it remains waterproof when winding the watch or even when setting the time. This addresses that common concern we frequently hear from audience members – they worry that a watch without a screw-down crown is susceptible to water intrusion should the crown accidentally be pulled out when in the water. The precisely engineered gasket-free design by Mauron Musy, the brand says, offers peace of mind while doing away with a screw-down crown.

Having no screw-down crown eliminates the dire possibility of messing up threads in a brief moment of carelessness and adds an extra level of comfort in that winding and setting the watch is quick and easy. A plus on a GMT watch designed for frequent travel – once life allows for that. That said, it gives me the wrong kind of chills to think of setting the time on a $13,900 watch underwater, so I personally would rather consider this an extra layer of safety as opposed to a toy to play with.

Anything else for the wearer to sense from the nO-Ring tech? From the way the crown looks, feels, and functions, there are no oddities whatsoever. In fact, the crown is remarkably smooth to wind and jumps into well-defined notches – though these are more a complement of the movement than of the gasket-free system.

The only visible reminder of the nO-Ring system is the rather cool-looking hinges in the four “corners” of the watch. What makes these components “cool” despite their static nature (you can’t open them for obvious reasons) is that they do look like tension-closed latches in hermetically sealed doors, like those on ships or submarines. Looking at them, one gets the sense of how the lug structure and the case profiles and then the other lug structures are pulled shut, tightly wrapping the bezel and caseback, and the sapphire crystals within.

In fact, you can see into the case for yourself. It is exceedingly rare for the wearer to be provided any sort of insight into the inner workings and construction of a watch case. Just by those aforementioned four hinges, the inner case is revealed, and that’s all the more pronounced on this black-cased version that its inner structure in gray. On the caseback side, one can even see the “double” crystal as is highlighted in blue on the image below: it is a narrow top set on a wider base, and it is the wider base that is clamped down by the outer flanges against the perfectly flat metal surface of the inner case.

Case Quality Worth A Closer Look

Although the reality is different, it is true that theoretically, every watch case on every $13k watch should be a thing of beauty and high complexity, something one can admire just like a finer mechanical movement. As I said four years ago in the first Mauron Musy review, this brand’s level of case production well and truly is at a level that is reminiscent of the precision seen in high-end watch movements. A major (and positive) difference is that things are blown up to greater proportions and you can actually touch, see, and appreciate them at a greater scale with a case as opposed to a hermetically sealed movement.

The case is crafted from lightweight titanium, machined to a level that is truly extraordinary when one compares it to most of the competition, such as the potato-like titanium cases by Panerai or Breitling (I have a titanium-potato Breitling so I speak from experience – and with great fondness). If you have a developed taste and eye for clinically well-made things, you’ll probably appreciate the case quality here. It isn’t as romantically beautiful as high-polished cases or long, sweeping polished edges are. But there is a certain tangible beauty to extremely accurately crafted components fitting together in almost uncanny precision.

It is true that nearly all luxury watches out there are machined and put together with amazingly small tolerances (5-15 microns, generally), but there still seems to be a way for the human eye and hand to perceive a difference achieved through imperceptible improvements. It just works that way, and the precision engineers of Mauron Musy apparently know how to get to this level. Just picking the GMT Sport up and feeling its sharp (but not too sharp) edges and lots of odd-for-a-case angles and shapes is enough for one to understand that this isn’t titanium case quality you’re getting anywhere in the four-figure range.

I have raved on about the case for long enough – but that’s only because it does, indeed, deserve it. The challenge watches with a trademark component face is to ensure the rest of the parts are up to par. It’s a sad thing to see dials or movements or straps or buckles show signs of budgetary limitations. I think the Mauron Musy GMT Sport could have had a noticeably lower price tag had it had a lower rent dial and movement, ultimately allowing it to compete in the sub-$10k segment, as opposed to in the mid-teens. But low-rent parts and low(er) price tag it has not, so let’s see how the rest holds up.

Dial & Legibility

The textured dial looks like melted lava up close. From afar, the rugged texture better complements the overall look than a glossy black lacquered dial likely would. From up close, the texture is acceptable but not amazing. The overall dial quality remains high though thanks to a combination of floating islands (these carry the texts and indices) and what car designers would call “negative spaces” – and you or I likely would refer to as “holes.” These openings are nicely made and are located at the 1, 5, 7, 9, and 11-hour positions and, in fact, reveal the date disc underneath.

Again, from afar, one couldn’t tell what made for the texture/fill inside these openings, but a closer look reveals fractions of the numerals printed over the date disc. Needless to say, as the date disc advances, every 24 hours the “texture” of these oblong indices changes, adding a minute playful element to the dial — a classier way of playing with the date than those wholly exposed date discs on TAG Heuer 01 models or the oddly extended date apertures on some Parmigiani (and other) watches. For a brand debuting only its second series of watches, this is an impressively elegant way of playing with watch design elements.

The review unit is claimed to have had a prototype bezel. All other components (rest of the case, the dial, movement, strap, buckle) are final quality.

While daytime legibility is great thanks to the intelligent use of large, shiny hands over a matte dial, the quality of luminescence does not quite reach the same level. Positives include a bright and homogenous glow, no blotchy areas or weak glow to report. Even the thin edges of the oblong cutouts have lume applied – again, typically the sort of detail we frequently see others cheap out on by just luming the main/regular numeral indices. The lume’s shortcoming is in the relatively brief period of the powerful glow when compared to some other pieces. In other words, the lightshow doesn’t last long, but there is enough luminescence to aid legibility in absolute darkness for hours after a charge with a powerful light source.

The MM01 Caliber By La Joux-Perret

Mauron Musy is proud of the fact that the GMT Sport’s MM01 movement is made by La Joux-Perret, the highly advanced movement manufacture that stands behind the modern iterations of Arnold & Son and Angelus. LJP is renowned for supplying a host of high-end Swiss brands seeking bespoke solutions compared to what a modular, tarted-up or otherwise modified ETA or Sellita caliber could provide.

And indeed, one need not be a scholar of haute horlogerie to see that this isn’t your ordinary level of finishing. With hand-refined anglage, plenty of complex plates and bridges, and shiny steel wheels, this does fulfill the requirements for watchmaking jewelry. The gray color applied throughout to bridges and plates adds a touch of serious modernism and helps highlight the polished edges and wheels even more.

In short, the MM01 is up right there with the finest-looking movements in this price segment. Specs aren’t too shabby, either: The modern and stable 4-Hz operating frequency comes with a weekend-arching 55-hour power reserve. More to the point, the 4-Hz frequency is combined with a balance wheel of the size more commonly used with a lower 3-Hz frequency – the added mass of a larger balance wheel brings positives to the rate consistency and timekeeping performance of a mechanical movement. However, movements have to be engineered from the ground up to support a larger balance wheel at this higher frequency – proof that La Joux-Perret is not polishing movement designs several decades old but has been busy creating ones from scratch in the last decade.

One criticism I would have with the MM01 concerns the slightly audible rotor. It isn’t the loudest out there, but I do wish movement rotors got to a point where they could operate in absolute silence. The MM01 caliber is more complex-looking and more refined than what you will find in just about any $13k watch from any of the big names out there. And so, while Mauron Musy is not a movement maker, it has managed to extract top work from one of the best Swiss suppliers out there.

Wearing Experience Of The Mauron Musy GMT Sport Watch

On the wrist, strangely enough, the first things that stood out to me were the eight polished, Y-shaped screw heads acting like tiny flickering mirrors, looking like cat’s eyes set inside the black case flanges, another expensive detail that is really apparent in low light, the sort of stuff we’d mention even on six-figure-priced watches.

Flick your wrist, and the generous thickness of the Mauron Musy GMT Sport becomes apparent. While its titanium construction might help keep physical heft down, the visual heft remains. Especially the thickness of the bezel stands out with its vertical wall standing over the case profile. If you don’t like thick watches, you are better off with a more formal GMT watch with a less complex case and lower water resistance. During the day, the thickness doesn’t become cumbersome or annoying as long as you wear it like you would any thick watch and not expect it to be proactively crawling under the sleeve of shirts or jackets.

Titanium is a big help, though. Just like my hefty titanium Breitling, the GMT Sport offers all the benefits of this lustrous transition metal. The watch sits flush against the wrist without a steel case’s heft wobbling it around and it feels warm to the touch soon after putting it on as opposed to the ice-cold feel of steel. I wouldn’t be saying this were it July, but since it’s December, this is a plus.



Each piece comes with a rubber and a leather strap in the box with tool-free quick-release pins built into both to make changing straps easy. Despite the complex case design, the Mauron Musy GMT Sport has a regular lug structure that should accommodate all standard straps. The integration is deep toward the case but the cutout depth-wise is rather shallow, so super thick straps may not be an ideal fit. Nevertheless, the deep integration is always a very noticeable aid in achieving wearing comfort and a wobble-free fit, plus it makes for a tidier look. On a personal note, I certainly would choose one of the colored leather straps (brown or green being a particularly good match) and a black rubber strap to get the most versatility out of this package.

Throughout daily wear, the 44mm-wide case feels good for all the aforementioned reasons. It measures 14.6 mm thick and 51 mm lug-to-lug. As for that latter measurement, the strap does not turn fully downward by the end of the lugs, so add another 3-4mm to that lug-to-lug to get a proper idea. On my 17.5cm in circumference wrist, I could do with a slightly shorter rubber strap than supplied.


Mauron Musy chose to play with the big boys in the pricey $13,000 segment of luxury watches, clearly an ambitious goal for a relatively new brand. However, with an annual output capped at 600 watches, Mauron Musy isn’t a small brand anymore, and the fact that its growing pains are over is reflected not only by that number but also by the thoroughly and genuinely impressive quality it has managed to attain. We have seen much, much greater brands flounder at getting every last darn detail right from dial through cases and movement finishing to straps.

By contrast, the Mauron Musy GMT Sport does look, feel, and wear like a watch only two shrewd engineers would accept. It’s a product made by product guys – and at a time when fancy red carpet events and other nonsense seems to be reserving an alarming capacity of some of the greatest names in the business, that might just suffice to sustain this small brand.

Hefty but good-looking and proportionate, and fitted with a novel waterproofing system and beautifully crafted case and movement, this is a remarkably low-compromise watch any brand would be proud to call its own. It is also a testament to what can be done with 100% Swiss-crafted products. The Mauron Musy GMT Sport as tested here is priced at $13,900 USD, while the other four versions cost $12,900. You can learn more about the nO-Ring system and the GMT Sport collection on the brand’s website.

Necessary Data
>Brand: Mauron Musy
>Model: GMT Sport Reference MU04-203
>Price: $13,900 as tested
>Size: 44mm wide, 14.6 mm thick, 51 mm lug-to-lug
>When reviewer would personally wear it: Daily, if I could swap it out for something thin and small every once in a while.
>Friend we’d recommend it to first: Not easily impressed, looking for quality from off the radar.
>Best characteristic of watch: Strong package. Beautifully engineered, inside and out, so much so that it becomes an important element of the wearing experience. Plenty of small and unique details.
>Worst characteristic of watch: The bezel could use some cut-outs or other small details to help disguise its height and make it blend with the rest of the case. The lume could last longer.

Advertising Message

Subscribe to our Newsletter