Introduction
The Bulgari Octo Finissimo ref. 103431 is a watch that defies expectations. At just 5.15mm thick, it holds the record for the thinnest automatic watch in production. But thinness alone does not make a great watch. Over a week of daily wear, I put this Italian icon through the paces of real life—commutes, dinners, and the occasional bump against a doorframe. The question: does ultra-thin translate to ultra-wearable?
Bulgari’s Octo Finissimo line, first launched in 2014, has become a benchmark for architectural design and micro-engineering. The ref. 103431 is the entry-level steel model, but there is nothing entry-level about its execution. From the faceted case to the integrated bracelet, every angle tells a story of precision. This review focuses on what matters most: how it feels on the wrist, how it reads at a glance, and whether it survives a week without a scratch.
As a daily-wear reviewer at Vivir, I prioritize lug-to-lug fit, legibility, and comfort. The Octo Finissimo promises all three. Let’s see if it delivers.
Manufacture History
Bulgari was founded in 1884 in Rome, Italy, as a jewelry house. Over the decades, it expanded into luxury watches, leveraging its design heritage. The Octo Finissimo line, introduced in 2014, marked a bold step into ultra-thin watchmaking. The collection has since broken multiple world records for thinness, including the thinnest automatic watch, the thinnest tourbillon, and the thinnest chronograph. The ref. 103431 is the purest expression of this philosophy: a simple, automatic time-only watch with a date, housed in a case that is both geometric and svelte.
Movement
At the heart of the Octo Finissimo ref. 103431 beats the in-house caliber BVL 138. This automatic movement is a marvel of miniaturization, measuring just 2.23mm in height. It uses a platinum micro-rotor to wind the mainspring, allowing the entire movement to sit flush within the ultra-thin case. The power reserve is a respectable 60 hours, and the frequency is 28,800 vph (4 Hz). The movement features 31 jewels and is beautifully finished with Côtes de Genève, circular graining, and beveled edges. While it is not COSC-certified, its real-world accuracy is excellent. The date complication is displayed at 3 o'clock via a small window, which is crisp and easy to read.
Specifications
- Case Diameter: 40mm
- Case Thickness: 5.15mm
- Lug-to-Lug: 47mm
- Case Material: Stainless steel
- Crystal: Sapphire (box-shaped, with anti-reflective coating)
- Water Resistance: 30 meters (splash-proof only)
- Lume: None
- Bracelet/Strap: Integrated steel bracelet with H-shaped links
- Clasp: Folding clasp with double push-button release
Wrist Feel
The Octo Finissimo ref. 103431 is remarkably light on the wrist. The steel case and bracelet weigh just 85 grams, making it almost imperceptible during wear. The 47mm lug-to-lug ensures it sits flat on a 6.5-inch wrist without overhang. The integrated bracelet tapers from 24mm at the lugs to 18mm at the clasp, providing a snug yet comfortable fit. The folding clasp is well-machined, with a secure double push-button release.
Comfort is where this watch shines. The thin profile allows it to slide effortlessly under a dress shirt cuff, and the polished chamfers on the case catch light without digging into the skin. The only minor drawback is the lack of micro-adjustment on the clasp—you’ll need to size it perfectly at purchase. Over a week, I forgot I was wearing it, which is the highest compliment for a daily-wear piece.
Accuracy
The BVL 138 movement, while not COSC-certified, performed admirably in real-world conditions. Over seven days, the watch gained an average of +4.2 seconds per day, with a maximum deviation of +6 seconds. This is well within acceptable range for a non-chronometer automatic. The 60-hour power reserve held up over a weekend off the wrist, though I recommend a winder if you rotate frequently.
Occasions
The Octo Finissimo is primarily a dress watch, but its bold design allows it to straddle formal and smart-casual settings. It pairs beautifully with a suit or a blazer, and the thin case means it never snags on cuffs. For sport or swimming, the 30m water resistance is a clear limitation—this is not a watch for the beach or pool. However, for daily office wear, dinners, and events, it is ideal.
Wrist Presence
4/5 – The Octo Finissimo commands attention through its sharp, faceted case and mirror-polished surfaces. Despite its thinness, it has a strong wrist presence that draws compliments without being ostentatious. The black sunburst dial and applied indices add depth, making it legible in most lighting conditions.
Reference Variants
The Octo Finissimo family includes several variants. The ref. 103431 is the stainless steel model with a black dial and integrated steel bracelet. The ref. 103432 swaps steel for titanium, offering a lighter, matte finish with a grey dial. The ref. 103433 is a rose gold version with a brown dial and alligator leather strap. Each variant maintains the same ultra-thin case and movement, but the materials change the character significantly.
Family References
Other notable models in the Octo Finissimo line include the Tourbillon (ref. 103434), the Chronograph GMT (ref. 103435), and the Octo Finissimo S (ref. 103436), which adds a screw-down crown and increased water resistance. These models share the same architectural DNA but push the boundaries of complications.
Other Notable Bulgari Watches
Bulgari’s catalog extends beyond the Octo. The Bulgari Bulgari is a classic round watch with a distinctive bezel engraving. The Serpenti Seduttori is a women’s collection with a snake-inspired bracelet. The Bulgari Aluminium offers a sporty, retro aesthetic. Each collection reflects the brand’s Italian flair and jewelry heritage.
Similar Watches
If you appreciate the Octo Finissimo’s ultra-thin profile, consider the Piaget Altiplano Ultimate Automatic, which is even thinner at 4.3mm. The Jaeger-LeCoultre Master Ultra Thin Date offers a more traditional dress watch experience with a similar thickness. The Vacheron Constantin Patrimony Automatic is another elegant alternative, though it lacks the Octo’s angular personality.
Homages
Due to the complex octagonal case and ultra-thin movement, there are no direct homages of the Octo Finissimo. The design is too intricate for budget manufacturers to replicate convincingly. If you want the look, you’ll need to invest in the real thing.
Investment Value
The Octo Finissimo ref. 103431 has an MSRP of $12,500. On the pre-owned market, examples in excellent condition sell for $8,000 to $10,000. The trend is stable, as the model is still in production and well-regarded. For collectors, it represents a solid hold—Bulgari’s ultra-thin watches have a dedicated following, and the steel version is the most accessible entry point. Auction history is minimal, as the watch is not rare, but it does appear in high-end watch auctions occasionally.
Service Interval
Bulgari recommends a service every 5 years. The cost is approximately $800, and service must be performed by an authorized Bulgari service center due to the specialized movement. The micro-rotor and thin components require expert handling.
Pros and Cons
Pros
- Ultra-thin profile (5.15mm) – slips under any cuff
- In-house micro-rotor movement with 60-hour power reserve
- Distinctive, architectural design that stands out
- Lightweight and comfortable for all-day wear
- Excellent finishing on case and movement
Cons
- 30m water resistance – not suitable for swimming
- No lume – legibility in dark is poor
- Integrated bracelet limits strap options
- Clasp lacks micro-adjustment
- High price point for a steel watch without chronometer certification
Final Verdict
The Bulgari Octo Finissimo ref. 103431 is a triumph of micro-engineering and design. It offers unparalleled thinness without compromising on comfort or legibility. While it is not a sports watch, it excels as a daily dress piece for the discerning collector who values innovation and style. If you can afford the entry price, this is a watch that will earn its place on your wrist.
