Some watches tell time and call it a day. The Brellum Duobox 39 TC Moonphase Chronometer tells time, then keeps going, stacking a complete calendar and a moonphase on top of a 12-hour chronograph inside a 39.5-millimeter polished steel case.
It’s a lot. Only 46 exist. Brellum builds each one in the Swiss Jura, sells it directly from its own site with no boutiques or middlemen in between, and numbers every rotor from 01/46 to 46/46.
A Full Calendar Crammed Into One Blue Dial
Start at the top. Day and month sit in twin apertures inside the 12 o’clock subdial, and a slim central hand sweeps the pointer date printed in a ring around the dial’s edge. That’s a lot of furniture. Brellum calls the color Night Blue, and the sunray finish shifts tone as the light moves across its stacked, multi-level surface. Diamond-cut Roman numerals mark the hours, each one filled with Super-LumiNova alongside the matching diamond-cut hands. Night changes it.
Super-LumiNova fills the hands and indexes, so the calendar stack still stays readable after dark, and the AR coatings on the domed box sapphire keep reflections from washing the blue out.
At 9 o’clock, a small subdial tracks day and night, because apparently the sky needed a shift schedule too. The blue stays blue.
Thirty-Nine Millimeters, Fifteen of Them Tall
It wears small. The 316L stainless case measures 39.50 millimeters across and 48 millimeters lug to lug, so the footprint stays closer to a slim dress watch than to a modern sports chrono. Steel, not titanium. Thickness tells the truer story. The case runs 15.20 millimeters thick with both crystals counted and 11.20 millimeters without them, with box-shaped sapphire on the front and an exhibition back showing the decorated movement inside.
The 21-millimeter lug width keeps strap swaps inside standard sizing.
Alternating polished and satin-brushed surfaces split the casework, so light breaks differently across the bezel, the case flanks, the lugs, and the big polished pushers. Brellum tests every watch to that 100-meter rating before it ships. Rain’s a non-issue.
The Rotor Wears a Gold Moon
Flip it over. The BR-751 automatic runs on a Valjoux 7751 base, COSC-certified as a chronometer, beating at 28,800 vibrations per hour with 46 hours of reserve, 25 jewels, and a stop-second function inside. The finishing goes past the spec sheet. Perlage covers the main plate, Geneva stripes cross the bridges, the screws are blued, and every visible metal surface wears rhodium plating beneath the sapphire.
A 3N gold moon rides on the rotor, textured like the real thing and matching the one on the dial.
Pull the crown and the seconds hand stops, which helps when a calendar this busy needs setting. The layout’s pure 7751. The Valjoux layout arranges the calendar, moonphase, and day/night displays around the chronograph, which is how the full set fits inside a 39.5-millimeter case at all. Every display earns its dial space.
Two Straps Before the First Wear
Every watch ships on a stainless steel bracelet, and a calf leather strap rides along in the box, cut in black or brown, whichever color the buyer picks at checkout, both included.
Two looks, standard. A polished deployant buckle closes the leather strap, and standard sizes run M, L, or custom for wrists that don’t read size charts at all. Bracelet for weekdays.
The calf strap dresses the same watch down for weekends, and getting both in the box beats ordering the second one later on its own at full price.
Sold Only by the People Who Built It
There’s no discount here. The figure on the cards, CHF 3,598.50, is the price outside Switzerland, where Brellum’s listed price drops its Swiss VAT and payment still runs in Swiss francs, start to finish.
No boutique markup, either. Francs, not dollars. Founder Sébastien Muller is a fourth-generation watchmaker, and the family line runs back to his great-grandfather Emile’s watchmaking atelier, opened in 1910. The brand still sells every watch itself, small batches shipped straight from the Jura with no dealer network, no distributor, and no retail markup in between.
Forty-six pieces is the catch. When a run’s capped that low, missing the window means the secondhand market, and Brellum’s direct-only setup leaves no dealer shelf or back door holding a spare. Miss it and it’s gone.
Buy it if a full calendar, a moonphase, and a COSC-certified chronometer inside 39.5 millimeters sounds like the correct amount of watch for the money. Skip it if a 46-piece cap and a direct-only Swiss checkout feel like homework before the watch even ships to you.