Skeleton watches: history, technique and Swiss brands

What is a skeleton watch?

A skeleton watch is a mechanical watch whose movement has been cut away so you can see through it. The watchmaker removes as much metal as possible from the main plate and the bridges, leaving only the frame the wheels, springs and balance need to work. Often the dial is gone too, or reduced to a thin ring for the hour markers. The result is a watch where the time display floats over the moving parts.

The terms get mixed up, so it helps to separate them. A true skeleton is openworked through the whole thickness of the movement: you can hold it up to the light and see through it. Openworked is the wider term. Audemars Piguet uses it for its skeletons, and it can also mean that only part of a dial or a bridge is cut away. An open-heart watch has just one opening in the dial, usually showing the balance wheel beating. Frederique Constant's Heart Beat and Hamilton's Jazzmaster Open Heart are open-heart watches, not skeletons. A sapphire caseback only shows the back of an ordinary, solid movement. And a few watches use sapphire crystal for the plates and bridges themselves, so the movement is transparent without being skeletonised in the classic sense.

Skeleton watches are almost always mechanical. Most are dress or luxury pieces, but today you also find sporty skeletons in steel, titanium and ceramic.

History of the skeleton watch

The skeleton watch was born in 18th-century France. The Paris watchmaker André-Charles Caron, who worked for King Louis XV, is often credited with the idea. Around 1760 he began cutting metal from the plates and bridges of pocket watches to show the mechanism. Few of his pieces survive, so the exact origin is hard to prove. In 1746 Caron had taken on a young apprentice, Jean-Antoine Lépine, who later became his son-in-law and also watchmaker to the king. Lépine went on to build much slimmer pocket watch movements and is seen as a major influence on Abraham-Louis Breguet.

From the late 18th century the technique spread across Europe, including the Geneva region. Watchmakers did not just remove metal; they decorated what remained with engraved scrolls, foliage and Gothic tracery. In the 19th century the skeleton pocket watch became a showpiece of luxury watchmaking and a prized collector's object. These watches were always rare, because every plate had to be pierced, filed and engraved by hand.

When wristwatches took over in the 20th century, the craft moved with them. Audemars Piguet made openworking one of its specialities and later set up its own department for it. Specialists sold their skills to bigger brands: the Swiss watchmaker Armin Strom opened his shop in Burgdorf in 1967 and was hired by leading houses to skeletonise small series of their watches by hand.

The quartz crisis of the 1970s and 1980s gave the skeleton a new role. Cheap, accurate quartz watches had nothing to look at inside. A skeleton showed exactly what the Swiss could do that a battery watch could not. Audemars Piguet invested heavily in openworking from the 1970s. In 1980 Corum launched the Golden Bridge, based on an idea by watchmaker Vincent Calabrese: a straight-line baguette movement suspended in a sapphire case. In 1984 Armin Strom presented his own collection of hand-skeletonised watches at the Basel fair. Openworking reached the Royal Oak in 1981, and in 1986 Audemars Piguet showed an openworked Royal Oak perpetual calendar.

From the 2000s the skeleton changed character. In 2001 Richard Mille presented the RM 001, a tourbillon whose skeletonised movement was meant to be part of the design. The brand later moved to titanium and carbon baseplates and, with the RM 56-01 in 2013, to a baseplate and bridges in sapphire. CNC machines and new materials made modern, three-dimensional openworking possible, with angular bridges instead of engraved scrolls. Brands such as Hublot, Roger Dubuis, Zenith and Armin Strom's successors built whole collections around it. At the same time the classic houses kept refining the ultra-thin skeleton.

• c. 1760 – André-Charles Caron in Paris is credited with the first skeletonised pocket watches.
• 1967 – Armin Strom opens his shop in Burgdorf and becomes known for hand skeletonising.
• 1980 – Corum Golden Bridge with its linear baguette movement.
• 1981 – openworking appears in the Royal Oak collection.
• 1984 – Armin Strom launches his own skeleton collection.
• 2001 – Richard Mille RM 001 with skeletonised tourbillon movement.
• 2013 – Piaget shows an Altiplano with a 2.4 mm automatic skeleton movement; Richard Mille RM 56-01 with sapphire baseplate.
• 2019 – Breguet Classique Tourbillon Extra-Plat Squelette with a 3 mm movement.
• 2022 – Audemars Piguet Royal Oak Jumbo Extra-Thin Openworked with the new calibre 7124.

Features and technology

Skeletonising is a balancing act. The more metal you remove, the more you see, but the movement still has to be rigid enough to keep the wheels aligned and the watch accurate. A good skeletoniser first decides which parts can lose material, then cuts, then finishes every new edge.

Hand skeletonising is the traditional method. The craftsman drills small holes, threads a fine piercing saw through them and cuts out each shape, then shapes the outlines with files. This can take hours or days per part. Machine skeletonising uses CNC milling, stamping, electrical discharge machining or lasers. It is faster and cheaper and allows complex 3D shapes, but a milling cutter cannot make perfectly sharp inside corners. Sharp inward angles are therefore one sign of hand work.

Finishing is what separates a fine skeleton from a cheap one. On a skeleton, every cut edge is visible, so it should be chamfered (bevelled, called anglage in French) and polished. On the best pieces the flat surfaces are black polished until they look dark or bright depending on the angle. Classic skeletons are often engraved by hand with floral or architectural motifs. Modern skeletons tend to use geometric bridges, contrasting coatings and materials such as titanium, carbon composites or sapphire.

Because most of the plate is gone, legibility is the classic weakness. Brands work around it with bold hands, luminous paint, a chapter ring or tinted sapphire. Skeleton movements also tend to be thin and delicate, so many are hand-wound or use micro-rotors or peripheral rotors to keep the view clear.

Famous Swiss skeleton watch models

• Corum Golden Bridge (1980) – the baguette movement in a sapphire case made the whole watch a skeleton and is still made today.
• Audemars Piguet Royal Oak Openworked – openworking in the Royal Oak since the 1980s; the 2022 Jumbo Extra-Thin Openworked uses the 2.7 mm calibre 7124.
• Richard Mille RM 001 (2001) – the first Richard Mille, a skeletonised tourbillon that set the tone for modern technical skeletons.
• Ulysse Nardin Freak (2001) – a watch with no dial, hands or crown, whose whole movement turns to show the time.
• Piaget Altiplano Skeleton – an ultra-thin skeleton; the 2013 Only Watch piece used a 2.4 mm automatic skeleton movement in a 5.34 mm case.
• Vacheron Constantin Métiers d'Art Fabuleux Ornements (2014) – four openworked and engraved pieces inspired by ornamental art, limited to 20 each.
• Breguet Classique Tourbillon Extra-Plat Squelette (2019) – a 3 mm skeleton tourbillon with gold bridges, engine-turned and chamfered.
• Roger Dubuis Excalibur Skeleton Double Tourbillon – star-shaped bridges and two tourbillons that define the brand's skeleton style.
• Girard-Perregaux Laureato Skeleton (2017) – a skeleton version of the integrated-bracelet sports watch.
• Jaquet Droz Grande Seconde Skelet-One (2018) – the brand's first skeletonised watch, built around its figure-eight dial layout.
• Zenith Defy Skyline Skeleton (2023) – the first skeleton in the Skyline range, with a star-shaped openworked movement.
• TAG Heuer Monaco Skeleton (2023) – the square Monaco with a skeletonised Heuer 02 chronograph movement.
• Tissot T-Complication Squelette – a hand-wound skeleton that brings the look to a much lower price level.

Skeleton watches on the pre-owned market

Skeleton watches vary more in value than almost any other type, because the label covers everything from mass-produced machine-cut movements to watches that took weeks of hand work. The brand, the movement and the quality of the finishing matter more than the word "skeleton" on the dial.

The most sought-after pieces come from houses with a long openworking tradition, such as Audemars Piguet, Vacheron Constantin, Breguet and Piaget, and from modern technical brands like Richard Mille. Hand-engraved skeletons, ultra-thin skeletons and skeleton complications such as tourbillons and perpetual calendars attract collectors. Signed work by known skeletonisers, for example early hand-skeletonised Armin Strom pieces, has its own following. Antique skeleton pocket watches from the 18th and 19th centuries are a separate market, where maker, condition of the movement and quality of the engraving decide.

Originality is critical. A watch skeletonised at the factory is worth more than a standard model that was later cut open by a third party. Complete sets with box, papers and service records help, as with any watch. Because the movement is on show, any scratch, rust spot or damaged edge on a bridge is visible and lowers the value.

What to check before buying or selling

• Factory or aftermarket: check that the skeleton version exists in the brand's catalogue and that the reference on the papers matches. Later skeletonised movements usually hurt value.
• Finishing: look at the cut edges with a loupe. Fine pieces have even, polished bevels; cheap ones show raw, flat or rough edges.
• Hand or machine: sharp inside corners and hand engraving point to hand work; rounded inside corners suggest machining.
• Condition of the movement: since you see everything, check for rust, dust, scratched bridges, bent wheels and marks from previous repairs.
• Service: ask when the watch was last serviced and by whom. Skeleton movements are delicate and need a watchmaker who handles them carefully.
• Open-heart or skeleton: make sure the description is correct. An open-heart watch should not be sold as a skeleton.
• Authenticity: skeleton dials are popular with counterfeiters, so read our guide on how to spot a fake watch.

What is your skeleton watch worth?

If you own a skeleton watch and want to know its value, send a few clear photos of the dial, the caseback and any papers for a free watch value estimate. For estates, insurance or a fine antique skeleton pocket watch, a written watch appraisal gives you a documented value.

Swiss skeleton watches brands A–Z

29 Swiss brands with skeleton watches in their current or historic range. Click a brand for its full history and value guide.

• Armin Strom – Skeleton Pure, One Week Skeleton
• Arnold & Son – UTTE Skeleton
• Audemars Piguet – Royal Oak Openworked, Royal Oak Jumbo Extra-Thin Openworked, Royal Oak Double Balance Wheel Openworked
• Breguet – Classique Tourbillon Extra-Plat Squelette
• Chopard – L.U.C XP Skeletec
• Christophe Claret – Maestro
• Chronoswiss – Opus
• Corum – Golden Bridge, Golden Bridge Automatic, Golden Bridge Rectangle
• Cyrus Genève – Klepcys Vertical Skeleton Tourbillon
• Franck Muller – Vanguard Skeleton
• Frederique Constant – Classics Heart Beat (open-heart)
• Girard-Perregaux – Laureato Skeleton
• H. Moser & Cie. – Streamliner Tourbillon Skeleton, Endeavour Tourbillon Skeleton
• Hamilton – Jazzmaster Skeleton, Jazzmaster Open Heart
• Hublot – Big Bang Unico Sapphire, Classic Fusion Aerofusion
• Jaeger-LeCoultre – Master Ultra Thin Squelette
• Jaquet Droz – Grande Seconde Skelet-One
• Maurice Lacroix – Aikon Skeleton, Masterpiece Skeleton
• Patek Philippe – Calatrava Skeleton 5180/1R
• Perrelet – First Class Double Rotor Skeleton
• Piaget – Altiplano Skeleton, Polo Skeleton
• Raymond Weil – Freelancer Skeleton
• Richard Mille – RM 001, RM 027, RM 56-01, RM 27-05
• Roger Dubuis – Excalibur Skeleton Double Tourbillon, Excalibur
• TAG Heuer – Monaco Skeleton
• Tissot – T-Complication Squelette
• Ulysse Nardin – Freak, Blast Skeleton Tourbillon
• Vacheron Constantin – Métiers d'Art Fabuleux Ornements, Overseas Perpetual Calendar Ultra-Thin Skeleton
• Zenith – Defy Skyline Skeleton, Defy Classic, Chronomaster Sport Skeleton

Other watch types

• Dive watches
• Pilot watches
• Dress watches
• Chronographs
• Military watches
• Sports watches
• Jewelry watches

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