Breguet celebrates a milestone by looking to the stars with the Classique Tourbillon Sidéral 7255, which is the brand’s first flying tourbillon and also dressed up with an aventurine enamel dial. The Tourbillon Sidéral is the brand’s latest anniversary edition – and the most complicated so far – coming after the Classique Souscription and more recent Type XX 2075BH.

Initial Thoughts

Abraham-Louis Breguet’s workshop only built between 40 to 49 tourbillons in his lifetime, explaining the mythical rarity of the mechanism in historical watchmaking. Now more tourbillons are built in a single day – possibly even by a single brand – than during Breguet’s entire lifetime. Consequently, the tourbillon is no longer regarded with the reverence it enjoyed for centuries.

Tourbillons aren’t inherently special today, but still have appeal when executed well; the whole of the parts can be more than the sum of the parts. The Tourbillon Sidéral is executed well and appealing. Flying tourbillon aside, the rest of the watch is very good, though not ground breaking.

As with Breguet’s other 250th anniversary models, the Tourbillon Sidéral is more interesting aesthetically than technically since the movement is derived from the longstanding Lemania calibre. That approach will change as the year’s end approaches as Breguet has something bigger in the pipeline. For now, the Tourbillon Sidéral is an excellent watch that may suffer under the weight of expectations, but perhaps unfairly so, since other brands receive kudos for doing less.

Putting the Stars in the Sky

On this day, 224 years ago, the French Ministry of the Interior granted A.-L. Breguet a patent for his most famous creation. Breguet’s invention rotated all the components most relevant to timekeeping along the same axis as the balance, theoretically giving the same rate across all vertical positions. It was a natural fit for chronometry trials using the Plantamour rating system, which emphasised consistency across positions and there the tourbillon built its reputation, certificate by certificate.

Breguet No. 1176. Image – Breguet

Fittingly, Breguet is marking its 250th anniversary with a tourbillon. Despite the name, the Classique Tourbillon Sidéral is largely a traditional tourbillon and not a tourbillon with an astronomical display.

Sidéral is not a reference to sidereal time, but instead the sparkly aventurine enamel dial, a first for Breguet. As an aside, the brand’s aventurine-esque moon phase disks found on its perpetual calendar models are blue lacquer, not aventurine glass.

Most watch brands buy sheets of industrially produced aventurine glass which is then cut and polished like a natural stone dial.

Breguet instead opted to make its own aventurine glass from scratch using a technique akin to grand feu enamelling. Raised rims along the dial perimeter and the apertures for the hands and tourbillon act as walls to contain the powdered glass and copper flecks as the dial is built up, painted layer by layer, and then repeatedly fired in a kiln at 800°C, one strata at a time.

All That Glitters is Gold

The Breguet hands, applied text, and tourbillon aperture frame are all solid 18k Breguet gold, a proprietary yellow gold alloy. Even the eccentric hour ring at 12:00, which carries Breguet numerals and the “secret signature,” is solid gold underneath the blue PVD coating.

The 38 mm case is also Breguet gold, and in return to its usual fare (unlike the Souscription), the case features the cold-rolled fluted case band and straight welded lugs. Each case is individually numbered out of 50.

Despite all of the precious materials on the dial, the centrepiece is the flying tourbillon. Surprising as it may be, this is in fact Breguet’s first flying tourbillon, a concept independently realized by English and then German watchmakers over a century ago.

The brand did have a historical model that resembled a flying tourbillon, but was not. The Classique Tourbillon Messidor 5335 of 2007 sandwiched the tourbillon between two clear sapphire disks, creating a levitating effect. The lower support of the cage was also sapphire, completing the illusion.

Breguet has revisited the Messidor’s movement for the Tourbillon Sidéral, transforming it into the cal. 187M1 with the brand’s first flying tourbillon.

Unlike A.-L. Breguet’s original invention, the flying tourbillon is supported on only one side, doing away with the upper bridge and providing a clear view of the cage. On the Tourbillon Sidéral, the tourbillon sits a full 2.2 mm above the movement, and even stands proud of the very thick dial, adding to the three dimensionality of the face.

An exploded view of the flying tourbillon assembly

The tourbillon cage rotates once per minute, acting as a de facto seconds hand. Inside is a free-sprung, screw-poised balance beats at a stately 2.5 Hz.

While Beguet has been a pioneer in silicon for many years, the Tourbillon Sidéral relies on a Nivachron metal alloy hairspring and escapement. Naturally, the Nivachron balance spring has a Breguet overcoil, and is blue to evoke the blued steel springs of the past.

The bridges and plates of the cal. 187M1 are solid 18k Breguet gold to match the case and dial furniture. The choice of gold is fitting as A.-L. Breguet chose rose gold rather than brass for perhaps his most famous work, pocket watch no. 160 that was allegedly made for Marie Antoinette.

Both the full plate and lower tourbillon bridge are engine turned with the “Quai de l’Horloge” guilloché found several of the 250th anniversary models, including the Souscription’s case back.

Like the Souscription, each Tourbillon Sidéral is accompanied by individually numbered red leather box that is unique to the anniversary editions. And the certificate of origin is signed by both Breguet chief executive Gregory Kissling and president Marc A. Hayek.

Key facts and price

Breguet Classique Tourbillon Sidéral
Ref. 7255BH/2Y/9VU

Diameter: 38 mm
Height: 10.2 mm
Material: 18k “Breguet” gold
Crystal: Sapphire
Water resistance: 30 m

Movement: Cal. 187M1
Functions: Hours, minutes, flying tourbillon
Winding: Manual wind
Frequency: 18,000 beats per hour (2.5 Hz)
Power reserve: 50 hours

Strap: Alligator strap with folding clasp

Limited edition: 50 pieces
Availability: First availability at boutiques, and subsequently at retailers
Price: CHF190,000 before taxes

For more information, visit Breguet.com.