Brellum shrinks its triple calendar moonphase chronograph to 39.5mm in blue

Brellum has introduced a blue-dial version of its Duobox Triple Calendar Moonphase Chronometer, this time inside a smaller 39.5mm steel case. Production is capped at 46 pieces, each priced at CHF 3,890. The brand quotes the price without VAT as CHF 3,600.

The case has a 48mm lug-to-lug span and 15.2mm total thickness, though the case itself measures only 11.2mm. Heavily domed sapphire crystals on the front and back account for the extra 4mm. Water resistance is 100 meters.

What the case and dial offer

The mid-case is brushed and the bezel polished, with pump-style chronograph pushers and a knurled crown on the right side. Curved lugs soften the profile, and the same five-row Jubilee-style bracelet from the regular Duobox 39 Chronometer holds it on the wrist.

Founder Sébastien Muller, a fourth-generation watchmaker, set up the Swiss independent brand in 2016. Brellum introduced the Duobox Triple Calendar Moonphase Chronometer in 2024, in the original 41.8mm case, followed by silver, opaline salmon and ice-blue dials.

A 39mm Duobox already existed, built around a La Joux-Perret column-wheel chronograph movement and later offered in pink and ice-blue mother-of-pearl. The complication-heavy version stayed at 41.8mm until now, so this watch joins the two lines.

The blue sunray dial has a multi-level construction, applied Roman numerals and three sub-dials in the classic Valjoux 7750 layout. At 12 o'clock, a 30-minute counter houses the day and month windows. The 6 o'clock totalizer, for 12 hours, incorporates the moonphase.

A calendar scale runs around the dial's edge, read by a central date hand. Running seconds and a day/night indicator share the 9 o'clock register. Branding moves to 3 o'clock, a change from the regular Duobox 39 Chronometer, where it is at 12.

The hands are filled with luminous material, and the color is restrained: blue against silver, with no contrasting accents. Buyers also receive a choice of black or brown calfskin strap with a folding clasp, alongside the steel bracelet with its hidden butterfly clasp.

The BR-751 movement

Inside is the BR-751 caliber, based on the automatic Valjoux 7751, the calendar version of the ubiquitous 7750. It is COSC certified, with a specified accuracy of +6/-4 seconds per day, and runs at 28,800 vibrations per hour on 25 jewels.

The power reserve is 46 hours. Decoration includes perlage, Geneva stripes and blued screws, visible through the sapphire caseback. The custom rotor carries a gold-coated moon and the watch's limited-edition number, so each one is individually numbered.

On the wrist the smaller case is better proportioned than its larger siblings. At 15.2mm it is slimmer than the 15.9mm of the bigger Duobox, and the domed crystal makes it look thinner still, though it remains a chunky watch that will not slide under a cuff.

The chronograph starts, stops and resets with firm clicks. Pulling out the crown sets the time and calendar, and a small corrector on the right side of the case adjusts the date in months with fewer than 31 days.

Brellum produces no more than 299 watches a year, so this 46-piece run is a small batch even by the brand's modest scale. The price is in line with the other watches in the Duobox series.

We have followed small independent makers like Brellum in our coverage of scene, where limited runs surface alongside the larger maisons. Here the numbered edition pairs a triple calendar and moonphase with a COSC chronograph, at the lower figure of CHF 3,600 before VAT.

The smaller case leaves room for more variants. The brand tends to issue fresh variations of its watches, and this blue model may be the first of several in the 39.5mm size. Orders run through the official Brellum website, brellum.swiss.