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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchThe Brellum Duobox Triple Calendar Moonphase Chronometer DB.CH.931 combines a full calendar, moonphase, day/night display and chronograph in a 41.8 mm steel case. Its launch configuration paired a decorated, COSC-certified automatic movement with a notably information-dense silver dial; the reported 46-piece edition was introduced in 2024.
How the dial organizes its many functions
The DB.CH.931 is built around the Valjoux 7751 layout: calendar and timing displays share the dial rather than being separated into distinct zones. The pointer date tracks around the outer perimeter, while day and month indications sit at 12 o’clock. At 9, a subdial combines running seconds with a day/night indication. At 6, the moonphase shares space with the 12-hour chronograph register; the 30-minute counter is incorporated into the 12 o’clock subdial. Central hands show the time, and a central seconds hand serves the chronograph.
The domed, multi-level silvered dial has a sunray finish and applied, diamond-cut indices. The central chronograph seconds hand and small subdial hands are blue. Fratello reports Super-LumiNova on the hour and minute hands. The layout asks the wearer to learn which indications share each subdial, but gives the watch its unusually broad range of information without resorting to a digital display.
Movement and chronometer credentials
Brellum’s automatic BR-751 is based on the Valjoux 7751. Launch specifications give it COSC chronometer certification, 25 jewels, a frequency of 28,800 vibrations per hour and a 46-hour power reserve. Visible through the display back, its reported decoration includes perlage, Geneva stripes, blued screws and a gold-toned, 4N-coated rotor.
#1 Best Overall
- 59 teeth gear for 29 ½ Days MoonPhase Display
- Gold Swan Neck
- Column Wheel Chronograph
- Blue steel screws
- Exhibition Case Back Cover
COSC certification is the documented accuracy credential; it should not be mistaken for a published independent test of this particular watch beyond that certification. For operating instructions, Brellum lists an English “User’s manual BR-751 Moonphase Chronometer (Valjoux base)” on its official user-manuals page.
Case dimensions and wrist presence
The stainless-steel case is specified as 41.8 mm across, 51.8 mm lug-to-lug and 15.9 mm thick, including the box-style crystals. It has a sapphire front crystal with antireflective coating and a screw-in steel caseback with a domed sapphire display window. Fratello’s specification table gives 41.8 mm for the diameter, although its accompanying prose says 41.5 mm; 41.8 mm is the more precise figure to use from that source, with the discrepancy noted.
Rank #2
- Case Size: 40.00 mm, Band Width: 20, Case Thickness: 7.62 mm
- Swiss quartz movement, 316L stainless steel case, Roman dial type, Date/moonphase
- Stainless bracelet, butterfly clasp with push-buttons closure
- Water-resistant up to a pressure of 5 bar (50 m / 165 ft): suitable for short periods of recreational swimming and showering, but no diving or snorkeling.
- 2 Year International Warranty
Those proportions make this a substantial dress-leaning chronograph rather than a compact calendar watch. Fratello reviewer Michael Stockton judged it large for smaller wrists, while finding the dial clean and legible after the functions were understood. Wrist fit remains personal: lug-to-lug length and thickness matter alongside diameter, so trying the watch on is the best way to assess how it sits.
Strap, water resistance and launch configuration
The reported launch configuration included a black alligator strap and Brellum deployant clasp. Monochrome said a stainless-steel bracelet could be requested, but that is a launch-era report, not confirmation of present availability. Check the exact lug width and clasp compatibility before choosing a replacement strap.
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Rank #3
- 59 teeth gear for 29 ½ Days MoonPhase Display
- Bi-directional Bezel
- Column Wheel Chronograph
- Blue steel screws
- Exhibition Case Back Cover
The published water-resistance figure is 100 m, reported as a manufacturer specification by watch publications. That rating alone does not establish suitability for a particular water activity.
What the 2024 launch details do—and do not—tell you
Fratello and Monochrome reported a launch price of CHF 3,690 and a numbered edition of 46 pieces. Fratello also listed a two-year warranty. Monochrome’s launch coverage said orders opened directly with Brellum on April 4, 2024, with deliveries scheduled to begin in May. These are historical launch details; they do not establish current stock, warranty coverage for a particular pre-owned watch, or its present resale value.
Rank #4
- Multifunction Design: Three multifunction small dials support stopwatch ,60-minutecounterand Moon phase , Calendar display, Luminous, full-featured service for you
- Details of the watch: Imported quartz analog movement and battery, Mirror Diameter 43MM, case thickness 13.5MM, band length: 200MM, weight 123G, water-resistant to 30M
- Details of the watch: Imported quartz analog movement and battery, Mirror Diameter 43MM, case thickness 13.5MM, band length: 200MM, weight 123G, water-resistant to 30M
- Glow In The Dark: When you need your watch to luminous,Please Illuminate the Watch Under the Strong Light for 30-40 Seconds to Activate the Luminous Function.Giving you a new visual experience at night
- Give for him: Fashionable and elegant design for any man who appreciates quality and style. Suitable for male college students, businessmen, gentlemen, business elites, leaders, colleagues, boyfriends, lovers, family members, sons, etc
The official Brellum shop page currently cited for a Duobox 39 concerns a different watch with the BR-110 movement, not this DB.CH.931; its price or availability should not be used as a proxy for the Triple Calendar Moonphase. See the separate Duobox 39 Chronometer page only to distinguish the models.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Who the DB.CH.931 suits
- Consider it if you want a mechanical watch that combines a full calendar, moonphase, day/night indication and chronograph in one display, and appreciate a traditional multi-register layout.
- Check carefully if you prefer a thinner or shorter-wearing watch, need an immediately simple dial, or are buying remotely without a chance to assess the case dimensions on your wrist.
- Before buying confirm that the listing is specifically for reference DB.CH.931, and verify its condition, included strap or bracelet, paperwork and any remaining warranty. Launch coverage does not confirm current availability.
In his April 4, 2024 Fratello hands-on, Michael Stockton wrote that the Valjoux 7751 execution is “clean and legible once the functionality is understood.” That assessment captures the watch’s central trade-off: a wide spread of useful indications in a large, layered display, with a learning curve that comes with the territory.
Best Value
- Swiss Made Watch
- Movement: Automatic Mido Caliber - Power reserve 60 hours
- Case Type: Stainless steel - See-through case back
- Case Size: 42mm - Band Width: 22mm - Case Thickness: 13.32mm
- Crystal: Sapphire crystal with double sided anti-reflection treatment
Sources: Fratello Watches, April 4, 2024; Monochrome Watches, 2024 launch coverage.
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Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
