Bulgari Octo Finissimo Ultra COSC: The World's Thinnest COSC-Certified Chronometer

Bulgari Sets New Record with Thinnest COSC-Certified Watch

In April 2024, Bulgari stunned the watchmaking world by unveiling the Octo Finissimo Ultra COSC — a remarkable feat of engineering that measures just 1.70mm thick, making it the thinnest mechanical watch on the planet. But what makes this achievement truly extraordinary is that the 1.50mm-thick BVL180 movement inside has passed the rigorous official chronometer tests administered by COSC (Contrôle Officiel Suisse des Chronomètres).

According to aBlogtoWatch, this marks a significant milestone in haute horlogerie, as highly complicated and ultra-thin watches are rarely subjected to independent accuracy testing. The Octo Finissimo Ultra COSC proves that extreme thinness and chronometer-grade precision can coexist.

Engineering Breakthrough: How Bulgari Achieved 1.70mm

To reclaim the thinness crown from Richard Mille, Bulgari shaved another 0.1mm off the original 2022 Octo Finissimo Ultra. The key innovations include:

• Tungsten carbide caseback that doubles as the movement's mainplate — eliminating the need for a separate plate
• Horizontal movement architecture developed with Concepto, spreading all components flat with minimal vertical overlap
• Separated winding and setting functions via two dedicated wheels instead of a traditional crown mechanism
• Running seconds displayed on a rotating disc — a requirement for COSC certification, positioned between the minutes subdial and balance wheel

The watch runs at 4Hz frequency with a remarkable 50-hour power reserve, exceptional for an ultra-thin construction. The 40mm titanium case features an openworked bracelet with a clasp that folds into the bracelet links, maintaining the ultra-slim profile.

Specifications at a Glance

Why COSC Certification Matters for Ultra-Thin Watches

The significance of COSC certification on the Octo Finissimo Ultra cannot be overstated. As noted by aBlogtoWatch, "the more complicated or complex luxury watches are rarely ever put through any form of proper independent testing for their performance." This means that many high-end watches — including tourbillons, minute repeaters, and perpetual calendars — are never verified for accuracy by an independent third party.

COSC certification requires a watch movement to maintain accuracy between -4/+6 seconds per day across multiple positions and temperatures over a 15-day testing period. Achieving this in a 1.50mm-thick movement demonstrates that Bulgari has mastered both the art and science of ultra-thin watchmaking.

The Competition for Thinnest Watch

The ultra-thin watch race has intensified in recent years. Richard Mille's RM UP-01 Ferrari briefly held the crown at 1.75mm before Bulgari's new Ultra reclaimed the title. Chopard's L.U.C Full Strike minute repeater is another example of a highly complicated watch that has achieved COSC certification, proving that accuracy and complexity are not mutually exclusive.

Frequently Asked Questions

What does COSC certification mean?

COSC (Contrôle Officiel Suisse des Chronomètres) is the official Swiss chronometer testing institute. A watch movement must maintain accuracy between -4/+6 seconds per day across multiple positions and temperatures over 15 days to earn COSC certification.

Is the Bulgari Octo Finissimo Ultra COSC wearable?

Yes. Despite its extreme thinness, the watch is designed to be worn. The tungsten carbide caseback provides structural rigidity, and Bulgari's philosophy is "if you can't wear it, it's not a watch." The 40mm case wears wide but comfortably on most wrists.

How does the power reserve compare to regular watches?

At 50 hours, the Octo Finissimo Ultra COSC offers a respectable power reserve for an ultra-thin watch running at 4Hz. Most standard mechanical watches offer 38-42 hours, making this a notable achievement.

Internal Links

• Learn more about watch certifications: COSC vs METAS vs in-house
• Explore our guide to the history of ultra-thin watches

Source: aBlogtoWatch, April 8, 2024