Thinness is the most underrated achievement in watchmaking. A tourbillon or a chronograph announces itself; a genuinely thin watch just disappears, and almost nobody claps. Bulgari has spent the last decade chasing it harder than anyone, setting one world record for thinness after another with the Octo Finissimo. The steel version here, reference 103431, is the part of that obsession you can actually live with: a 6.4mm case, a 2.23mm movement, and, just as important, 100 meters of water resistance and a screw-down crown, so the thinnest watch in the room is also one you could wear to the pool.
The brief
The satin-polished steel Octo Finissimo with blue sunburst lacquer dial, integrated steel bracelet, and BVL 138 microrotor movement. 40 mm width, 6.40 mm thickness, screw-down crown with ceramic insert, 100 m water resistance. The "S" steel iteration adds real-world durability while keeping the collection's calling card: thinness as a feature in its own right.
Case and finishing
On the wrist, Bulgari's layered octagon looks less like a watch than a small piece of architecture. The satin and polished facets catch light without shouting, and the step bezel reads cleanly at arm's length and holds up under a loupe. The headline is still the 6.4mm case: thin enough to slide under any cuff, but with the screw-down crown and 100m rating it never feels like the wafer it photographs as.
Link articulation is tight and even. If you do the "over-the-finger" test, the bracelet drapes uniformly rather than collapsing in sections, the kind of detail watch geeks obsess over.
Dial and legibility
Blue lacquer with a sunburst finish that runs radially from center. Applied rhodium markers and Arabic numerals at 12 and 6 keep the dial from going flat; skeletonized hands fit the theme. No date, no minute hashes. Result: clean look, quick reads, but setting to the exact minute takes patience. Also no lume: note this if you want night visibility.
Movement: BVL 138 Finissimo
The architecture is a 2.23 mm-thin automatic with a platinum microrotor and small seconds at about 7:30, running at 3 Hz with a 60-hour reserve. The finishing is restrained but coherent: wide striping, neat anglage on the balance bridge, and a dense microrotor that adds visual weight. The caliber does not hack; you can back-set to align the seconds, but there is no true stop-seconds. The microrotor is the point of pride, and it is fundamental to how thin the watch can be.
Bracelet and clasp
Integrated steel bracelet with a butterfly-style deployant that sits flush and adds almost no visual thickness. There's no push-button release and no micro-adjust; fine sizing relies on small links rather than on-the-fly adjustment. Comfort is excellent once sized, though hot-cold wrist changes may send you a half-link hunting.
On the wrist
The watch disappears under a shirt and feels like a cuff: broad, flat, stable. The blue dial shifts from inky to electric depending on light, giving the otherwise minimal layout some life. As discussed on A Matter of Time, thinness genuinely functions like a complication here: you feel the engineering every time the bracelet articulates. "Just go to a store and try an Octo Finissimo - you'll get the feeling."
Comparisons
Could be compared to the Royal Oak 15510 or the Nautilus 5711 lineage. The Octo plays a different game stylistically yet competes on finishing of the case and bracelet and everyday wearability. Time+Tide positioned this exact ref as the best modern challenger during its launch year, a fair framing if you want integrated steel without a years-long wait list mindset.
You buy the steel Octo Finissimo for the experience of wearing the thinnest watch in almost any room without having to baby it. The price of admission is a short list of inconveniences: no lume, no hacking seconds, and a bracelet you size with patience rather than a click. None of them matters much once it is on the wrist. For a watch this thin that you can still swim in, that is a fair trade.
Specs at a glance
- Case: 40 mm width, 6.40 mm thick, satin-polished steel, screw-down crown with ceramic insert, sapphire front and back, 100 m WR
- Dial: Blue lacquer, sunburst, applied indices and 12/6 numerals, small seconds ~7:30
- Movement: BVL 138 microrotor automatic, 3 Hz, 60-hour power reserve, 2.23 mm thick
- Bracelet: Integrated steel, butterfly clasp, no micro-adjust
- Notable changes vs early Finissimo: water resistance up from 30 m to 100 m with a small thickness tradeoff, improved daily utility.
References
- Bulgari official spec page for Ref. 103431 - case 6.40 mm, 100 m WR, BVL 138 with platinum microrotor, blue sun-brushed lacquer dial with rhodium applied indexes. (Bulgari)
- Fratello - launch coverage and spec sheet for Ref. 103431 - 40 mm, 6.4 mm, 100 m WR, price context at launch. (Fratello Watches)
- Time+Tide - hands-on impressions of the blue dial steel ref - dial tone, bracelet feel, and competitive framing versus RO/Nautilus. (Time+Tide Watches)
- Monochrome - movement dimensions and technical notes - BVL 138 at 2.23 mm, 3 Hz, 60 h. (Monochrome Watches)
- Fratello "Why I Bought the Octo Finissimo S" - notes on non-hacking, minute-track precision when setting. (Fratello Watches)
- A Matter of Time, Episode 4 (YouTube) discussing bracelet tolerances, thinness as a "complication," and try-on experience.
