Montblanc has unveiled a new interpretation of its haute de gamme suspended Exo Tourbillon model from 2018. This new timepiece is the Star Legacy Exo Tourbillon Skeleton LE8 featuring a heavily open-worked movement with the characteristic balance wheel floating atop the tourbillon cage.

The “Exo” in the Exo Tourbillon is a reference to the large balance wheel with screws, which is positioned outside of the tourbillon’s rotating cage. Exo is Greek for outside or external. The watch has a unique construction allows for use of an imposing balance wheel to be the star of the show, relegating the mighty tourbillon to a supporting cast role. A bigger balance wheel ensures a stable accuracy rate. This watch is part of the  Star Legacy line, a family of classically-styled watches take their style cues from Minerva pocketwatches made during the end of the 19th and the beginning of the 20th century. 

All this openworked wizardry but do not miss the grand feu enamel dial

It uses an imposing 44.8 mm 18K rose gold case that’s 15.01 mm thick and fitted with a domed sapphire crystal on the dial side and an exhibition caseback to allow for 360 degree views of the three-dimensional skeleton movement. It is fitted with an 18K rose gold onion crown with the Montblanc emblem in mother-of-pearl, the case is water-resistant to 30 meters.

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The openworked movement’s architecture is dominated by a suspended balance wheel that anchors the whole show. Suspended by a steel cock, the imposing 14.5 mm balance wheel does its thing above the tourbillon’s mirror-polished rotating cage – see, this is how Montblanc puts the Exo in Exotourbillon by placing the balance wheel outside of the tourbillon. The tourbillon takes a minute to complete one rotation thus also marking the passing of seconds on the tourbillon bridge.

Notice how the tourbillon bridge has only arm

Opposite it is an 18K gold dial with grand feu enamel dial with Breguet numerals and slim rose gold hands. The heavily skeletonized movement has a three-dimensional quality to thanks to five pillars that support the main plate on the top, and the barrel and gear train bridges. The main plate and bridges have been completely open-worked, making them visible on both sides of the watch, the barrel drum too is opened to reveal the mainspring.

Montblanc says it took its engineers 18 months to develop this new movement. The Manufacture Calibre MB M18.69 is made up of 188 components that are entirely hand-finished at the Villeret atelier, which used to be the Minerva factory. Except to see finishing techniques like circular graining, mirror-polishing, and beveling. The open-worked rhodium-plated German silver bridges have hand-chamfered edges, the gold-plated wheels of the gear train have a circular grained finish and chamfered edges and diamond hubs on both sides.

The mirror-polished winding pawl is shaped with the Minerva arrow

In addition, the movement also has 420 inner angles that can only be polished by hand. A hallmark of haute horology movements, these sharp inner angles are formed at the intersection of two chamfered surfaces and generally elicit oohs and aahs from the watch cognoscenti. Due to the level of skeletonization and decoration, assembly requires dexterity and care in order to avoid scratches on the beveled components. The Villeret manufacture also creates the full regulating organ in-house, including the hairspring, on-site.  

Limited to just eight pieces, the timepiece is fitted with a brown Sfumato alligator leather strap sourced from the Montblanc Pelletteria in Florence and is equipped with a triple folding clasp with security pushers, offering a secure grip.