Brellum’s latest Duobox is the sort of watch that reminds you how much mechanical watchmaking can still fit into a modest footprint.
The new Duobox 39 TC Moonphase Chronometer brings the brand’s triple calendar and moonphase layout into a 39mm case, pairing old-school calendar-watch charm with a fully fledged 12-hour chronograph.
For a small independent Swiss brand, it’s a confident move, especially in a segment where complicated chronographs often drift into much larger territory.
At a glance
- Brellum has introduced the Duobox 39 TC Moonphase Chronometer, a limited 39mm triple calendar moonphase chronograph.
- The watch combines a blue sunray dial, 12-hour chronograph, day, date, month, moonphase and day/night indication.
- It is limited to 46 pieces and priced at CHF 3,600 without VAT.
A smaller Duobox with a busier brief
Brellum was founded in 2016 by fourth-generation watchmaker Sébastien Muller, and the Duobox has been central to the brand from the beginning.
The original concept was defined by a pair of box-shaped sapphire crystals, one over the dial and one over the movement, giving the watch its distinctive domed profile from both sides.
Early Duobox models used a 41.8mm steel case with piston-style pushers and a COSC-certified Valjoux 7750 movement, later joined by the racing-leaning Duobox Pandial Chronograph.
The collection became more compact with the 39mm Duobox, and this new TC Moonphase Chronometer now brings the more elaborate calendar-and-moonphase personality into that smaller format.
The steel case measures 39mm across and 48mm from lug to lug, with a total thickness of 15.2mm including the domed sapphire crystals.
Without those crystals, the case itself measures 11.7mm, which helps explain how the watch keeps a relatively compact footprint despite the complexity inside.
The finishing mixes brushed and polished surfaces, with a polished bezel and the familiar piston-style chronograph pushers keeping the Duobox family resemblance intact.
Water resistance is rated at 100 metres, which is useful for a complicated chronograph that’s likely to be worn rather than kept as a dress-only piece.
The blue dial does a lot of work
The dial is blue with a sunray finish, using a multi-level construction that gives the display some needed depth.
Diamond-cut Roman numerals and hands continue the more classical language already seen on larger Brellum models.
There is a lot happening here, but the layout is logical once you know where to look.
The day and month displays sit at 12 o’clock inside the 30-minute chronograph counter.
The date is indicated by a central hand pointing to a scale around the outer edge of the dial.
At 6 o’clock, the sub-dial combines the 12-hour chronograph counter with the moonphase display, while the day/night indicator sits at 9 o’clock.
It’s not a minimalist watch, and it isn’t trying to be one.
The Roman numerals add visual density, but they also suit the traditional character of a triple calendar moonphase chronograph.
A COSC-certified Valjoux-based movement
Inside is the Brellum BR-751 automatic chronometer, based on the Valjoux 7751, the calendar-equipped relative of the 7750.
The movement is certified by COSC, runs at 28,800 vibrations per hour and offers a 46-hour power reserve.
Brellum has decorated the calibre with perlage, Geneva stripes and blue screws, visible through the exhibition caseback.
The rotor is 4N-coated and carries a moon-inspired design, with each rotor individually numbered.
The watch is supplied with a steel bracelet and one handmade calf leather strap, available in black or brown.
That combination gives the piece some useful range, from a more formal calendar-watch look on leather to a sportier feel on steel.
Details & Specifications
| Brand | Brellum |
|---|---|
| Model | Duobox 39 TC Moonphase Chronometer |
| Case size | 39mm diameter, 48mm lug to lug |
| Case material | Steel |
| Thickness | 15.2mm total, 11.7mm case without crystals |
| Crystal | Domed sapphire crystals front and back |
| Dial | Blue sunray, multi-level construction |
| Movement | Brellum BR-751 automatic chronometer, based on Valjoux 7751 |
| Certification | COSC chronometer-certified |
| Functions | 12-hour chronograph, triple calendar, moonphase, day/night indicator |
| Frequency | 28,800 vibrations per hour |
| Power reserve | 46 hours |
| Water resistance | 100 metres |
| Strap or bracelet | Steel bracelet plus handmade calf leather strap in black or brown |
| Production | Limited to 46 pieces |
| Price | CHF 3,600 without VAT |
The Duobox 39 TC Moonphase Chronometer is aimed at collectors who like practical complications, visible mechanics and independent production without moving into oversized case dimensions.
With Brellum making no more than 299 watches a year, this 46-piece release keeps the brand’s small-batch character intact while giving the Duobox 39 its most complicated expression yet.
