The Brellum Duobox 39 Triple Calendar Moonphase Chronometer Debuts In Blue
Over the years, Brellum has impressed us with small-batch, vintage-inspired watches, particularly chronographs. Within the brand’s modest collection, the Duobox series is my favorite. Its retro styling has plenty of charm, and founder Sébastien Muller keeps the lineup interesting with regular new variations. The latest is the Brellum Duobox 39 Triple Calendar Moonphase Chronometer in blue. It follows several versions of this complicated chronograph, all with larger cases. I had a chance to find out more about this new limited edition.
Brellum introduced the Duobox Triple Calendar Moonphase Chronometer in 2024. Mike reviewed the original silver-dial model, which was followed by a version with an elegant opaline salmon dial. Earlier this year, Muller unveiled an ice-blue version, which remains my favorite. This latest release introduces a new blue dial, but the more significant change is the smaller case — an update many enthusiasts will welcome with open arms.
The details of the Brellum Duobox 39 Triple Calendar Moonphase Chronometer in blue
The new Duobox 39 Triple Calendar Moonphase Chronometer features a 39.5mm stainless steel case with a 15.2mm total thickness and a 48mm lug-to-lug. It also offers a 100m water resistance rating. Brellum uses the same case for its regular Duobox 39 Chronometer, so the design will look familiar. The thickness might seem intimidating, but the case itself measures just 11.2mm thick. The heavily domed sapphire crystals on the front and back account for the extra 4mm, making the overall measurement less daunting than it first appears.
The mid-case features a brushed finish, contrasted by a polished bezel. On the right side are pump-style chronograph pushers and a knurled crown. The curved lugs add elegance to the profile and help soften the watch’s substantial proportions.
A vibrant blue dial
The case frames a rich blue sunray dial with applied Roman numerals and three sub-dials arranged in the classic Valjoux 7750 layout. There is quite a bit of information to take in. The sub-dial at 12 o’clock combines a 30-minute chronograph counter with the day and month displays. At 6 o’clock, the 12-hour chronograph totalizer incorporates a moonphase display. Finally, the register at 9 o’clock shows the running seconds and a day/night indicator. A calendar scale runs around the dial’s periphery.
Unlike the regular Duobox 39 Chronometer, this model has its branding at 3 o’clock rather than 12, accommodating the different dial layout. The hands are filled with luminous material, while a sharp central chronograph seconds hand and date indicator complete the display. I like Muller’s restrained use of color. The combination of blue and silver works beautifully, and contrasting accents would detract from the dial’s classy appearance.
The Valjoux-based Brellum BR-751
Inside is the same Brellum BR-751 caliber found in the larger Duobox Triple Calendar Moonphase Chronometer. Based on the automatic Valjoux 7751, this chronograph movement is certified by the Official Swiss Chronometer Testing Institute (COSC), with a specified accuracy of +6/-4 seconds per day.
The BR-751 operates at 28,800 vibrations per hour, has 25 jewels, and provides a 46-hour power reserve. Its custom rotor features a 3N-gold-coated moon and the watch’s limited-edition number. The finishing includes perlage, Geneva stripes, and blued screws, and the case back’s sapphire display lets you admire the movement when the watch is off your wrist.
Brellum fits the watch with the familiar five-row bracelet also used on the regular Duobox 39 Chronometer. Its Jubilee-style design and hidden butterfly clasp complement the watch nicely. Buyers will also receive their choice of a black or brown calfskin strap with a folding clasp.
Wearing the Brellum Duobox 39 Triple Calendar Moonphase Chronometer Blue
On the wrist, this smaller Duobox 39 feels better proportioned than its larger siblings. It is also slightly thinner. The difference between 15.2mm and 15.9mm is modest, but every little bit helps with the overall balance. That said, this is still a chunky watch that won’t easily slide under a cuff. It does, however, have plenty of wrist presence, and I enjoyed looking down at it whenever I wore it. The blue dial and silver details are a winning combination.
The build quality further enhances the experience. The watch feels well made and sits comfortably on the wrist, with the bracelet keeping it securely in place. The domed crystal also makes the case appear thinner than its measurements suggest. Operating the watch reinforces that impression of quality. The chronograph starts, stops, and resets with firm clicks. Pulling out the crown allows you to set the time and adjust the calendar, while a small corrector on the right side of the case handles the date in months with fewer than 31 days.
Final thoughts on the new Brellum Duobox 39 Triple Calendar Moonphase Chronometer Blue
Overall, I prefer this new 39.5mm version to its larger siblings. Though I still favor the ice-blue dial of the earlier model over this new, darker blue sunray one, the smaller case is undeniably appealing. The reduced dimensions improve its proportions and make it more wearable, even if its substantial thickness remains a consideration.
The introduction of a 39.5mm Duobox Triple Calendar Moonphase Chronometer also leaves room for future variations. Brellum regularly releases new versions of its watches, so this blue model could be the first of several. Production is limited to 46 pieces, each priced at CHF 3,890. That’s in line with the other watches in the Duobox series. In return, buyers get an attractive, complicated chronograph from an independent Swiss brand. If you’re interested in ordering one, visit the official Brellum website.
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