The independent French brand Yema has been steadily expanding its manufacture movement offerings in recent years, and among its in-house designs is the Caliber Manufacture Morteau 20 micro-rotor movement (better known as the CMM.20), which first made an appearance a couple of years ago inside the brand’s Wristmaster Traveller integrated bracelet watch. Since its introduction, the Yema CMM.20 has slowly started to appear inside an increasing number of models, and among the brand’s recent releases for 2024 is the Yema Navygraf Slim CMM.20 Limited Edition, which is a trimmed-down version of the popular Navygraf diver that is powered by the French brand’s very own manufacture micro-rotor movement.

Crafted from 316L stainless steel with linear brushed surfaces and high-polished bevels, the case of the Yema Navygraf Slim CMM.20 Limited Edition (ref. 22.24.66.SN.L6) takes advantage of its micro-rotor movement’s thin architecture to create a sleeker and more refined version of the brand’s popular vintage-inspired dive watch. Measuring 39mm in diameter by 9.5mm thick, the case is fitted with a double-domed sapphire crystal that brings the total height of the watch up to approximately 12mm, and its faceted lugs are set 19mm apart and extend to create an overall lug-to-lug profile of 46mm. Rather than aiming for the thinnest possible design, the Navygraf Slim CMM.20 simply intends to be a more slender rendition, and its revised proportions offer a noticeably thinner on-wrist experience, while still providing much of the same vintage-inspired charm that has made the Navygraf series a favorite among enthusiasts.

Surrounding the prominently domed sapphire crystal on the Yema Navygraf Slim CMM.20 Limited Edition is a 120-click unidirectional rotating timing bezel that is fitted with a black sapphire insert, and the bezel’s white luminescent markings offer a rather minimalist design with small dots and dashes at the cardinal points, plus an inverted triangle to signify the zero-marker. A signed screw-down crown sits between two beveled guards at the 3 o’clock location while a screw-down caseback with a large sapphire display window closes up the reverse side of the watch, and despite offering a noticeably thinner overall structure, the Yema Navygraf Slim CMM.20 still provides users with a rather generous 300 meters of water resistance.

For those curious about weight, the Yema Navygraf Slim CMM.20 Limited Edition comes in at approximately 61.5 grams (or 74 grams if you factor in its included leather strap), and its thin design combined with the large flat surface of its caseback results in a low center of gravity that evenly distributes the weight of the watch across the upper surface of the wearer’s arm. Additionally, while the wide bevels on the case of the Navygraf Slim CMM.20 help to minimize its visual presence by creating a more streamlined overall profile that hugs the top surface of the wrist, they also provide more space to grip the rim of the bezel, and this allows it to remain fairly easy to operate, despite having a relatively small outer textured rim.

The Yema Navygraf Slim CMM.20 Limited Edition is fitted with a black lacquer dial that offers a symmetrical time-only display, and it is furnished with applied luminous hour markers, white printing, and the “Navygraf” name in bright yellow letters above the hands. The baton-shaped hour and minute hands feature a polished steel finish to match the surrounds of the hour markers, while the needle-shaped seconds hand is bright yellow to complement the splash of color on the dial. Additionally, sitting at the very bottom below the 6 o’clock maker is the “MANUFACTURE FRANÇAISE” signature to denote the French origins of its movement and other locally manufactured components, and all of the luminous material that appears throughout the dial, hands, and bezel insert is Super-LumiNova BGW9 to create a bright blue-glowing display in the dark.

Although the thinned-down proportions of the Yema Navygraf Slim CMM.20 Limited Edition are certainly among its most noteworthy features, the real party piece of this particular model is its Caliber Manufacture Morteau 20 automatic movement, which is France’s very first ultra-thin micro-rotor manufacture caliber. Consisting of 190 individual components, the 33-jewel Yema CMM.20 is 80% French-made and 20% Swiss-made, and while all of its plates and bridges are manufactured at Yema’s Morteau-based workshops, the CMM.20 uses Swiss regulatory organs, such as its balance wheel and hairspring. Fitted with a bearing-mounted tungsten micro-rotor for optimal winding efficiency, the CMM.20 offers a modern and industrial appearance, and on the Navygraf Slim CMM.20 Limited Edition, the movement’s plates and bridges are finished black using an atomic layer deposition (ALD) process.

In addition to the pure horological novelty provided by a micro-rotor movement, having the automatic winding assembly positioned on the same plane as the gear train results in an inherently more slender overall structure, and Yema’s CMM.20 micro-rotor movement measures just 3.7mm thick, which makes it approximately 26% thinner than a standard ETA 2824. Adjusted to four positions, the Yema CMM.20 operates at a frequency of 28,800 ph (4 Hz) with a power reserve of approximately 70 hours, and while it doesn’t include the convenience of a hacking seconds mechanism, it does promise rather respectable timekeeping tolerances of -3/+7 seconds per day, which is very close to what is required for traditional chronometer certification.

Fitted to the lugs of the Yema Navygraf Slim CMM.20 Limited Edition is a black two-piece strap made from grained leather, which tapers from 19mm at the case down to 16mm where it connects to a signed stainless steel pin buckle. From an aesthetic perspective, the leather strap certainly suits the vintage-themed styling of the watch, and it ultimately offers a rather comfortable on-wrist experience with very little break-in time required. That said, I can’t help but slightly wish that Yema had opted for a strap material that was a bit better suited for aquatic conditions, and a simple tropic-style rubber strap (or even including an additional NATO with the watch) would have allowed users to take full advantage of the model’s ample 300 meters of water resistance.

Despite being powered by a thoroughly modern micro-rotor movement, the Yema Navygraf Slim CMM.20 Limited Edition is packed full of vintage-inspired design details that allow it to offer a lot of the same retro-style charm that draws people to mid-century dive watches. The glossy black surface of the dial amplifies the reflections created by the domed edges of the crystal, and the polished black bezel insert is reminiscent of the acrylic and bakelite bezels that can be found on vintage divers that were produced more than half a century ago. However, both of these components are made from sapphire on the Navygraf Slim CMM.20 for superior resilience, and the entire watch is characterized by a noticeably more solid and robust construction that is befitting of its manufacture French micro-rotor caliber.

In-house movements are often one of the most significant ways for watch brands to separate themselves from the competition, although it is often cost-prohibitive to produce a bespoke caliber, especially when operating on the more attainable side of the price spectrum. With that in mind, although Yema’s watches with manufacture movements are categorically more expensive than its offerings that are powered by third-party calibers, the actual price premiums are relatively reasonable, and the Yema Navygraf Slim CMM.20 Limited Edition (ref. 22.24.66.SN.L6) has an official retail price of $1,990 USD, with production limited to 200 examples. Given that you are getting a dive watch with 300 meters of water resistance and France’s first micro-rotor manufacture caliber, the Navygraf Slim CMM.20 represents a rather compelling offering, and I imagine that we will continue to see the CMM.20 micro-rotor movement play an increasing role within Yema’s catalog. For more information on the Yema Navygraf Slim CMM.20 Limited Edition, please visit the brand’s website.