The concept of skeletonisation goes right back to the basics of how you build a watch movement. Until the French watchmaker Jean-Antoine Lépine, in the 1760s, hit upon a radical idea for making pocket watches thinner, we didn’t have the basic model of plates and bridges that persists today (and still technically carries his name, even though almost nobody makes a movement that’s not a Lepine calibre).

It was a matter of no time at all before Lépine’s former master (and father-in-law) André-Charles Caron realised you could juice up customers’ interest in watches by revealing more of the mechanism. The clients at the time were Parisian courtiers, but when the watch industry found itself on the path to revival in the 1980s and early 1990s, it was the same story.

A tiny number of wristwatches had been skeletonised before - Vacheron Constantin’s archives speak of an openworked ultra-thin watch (with no engraving) from 1964 and a series run of the caliber 1003 in 1970, but in general the idea took hold as brands emerged from the quartz crisis.

Cartier Rotonde de Cartier Mystery Openworked
Cartier’s "Mysterious" watches make use of skeletonisation in a very modern way
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For about twenty ideas skeletonised watches enjoyed a heyday, of sorts. The combination of diligent handcraft and the inevitably baroque, grandiose style of the resulting creations was perfect for an industry restablishing itself as a luxury product.

And there’s no doubt that done well, they are utterly marvellous to gaze at through a loupe or catch the light with a swish of the wrist. The grandes maisons of horology embraced skeletonisation as they did the other great decorative skills - enamelling, engraving, gem-setting and finissage.

As with those other disciplines, skilled workers were scarce, and some artisans found themselves in high demand. Armin Strom, at the time a provincial restoration watchmaker working on his own creations in his spare time, showed his first skeletonised watch at Baselworld in 1984. It was to become the backbone of his career; by the end of the decade he was skeletonising everything from Omega Speedmasters to dress watches, and would go on to found his own brand in 2006 with openworking and skeletonisation at its heart. Another prominent skeletoniser, Jochen Benzinger, continues to work his craft as a customiser of other brand’s watches as well as creating his own intricate skeleton designs from new-old-stock movement.

Arnold & Son mainplate
An openworked Arnold & Son mainplate
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What's in a name?

As is often the case with watches, one has to decide how pedantic to be on the subject. Skeletonisation as it was traditionally understood refers to the modification of a calibre by removing unnecessary metal from plates and bridges. The vast majority of modern “skeletonised” watches never began life as a full-bodied movement, but looking at them, you must admit they are nothing if not skeletal. “Openworked” is often used instead, but is sometimes taken to imply a distinction between watches through which you can see clear daylight and those that merely have no dial. “Skeleton” remains the industry’s choice, but that has as much to do with marketing as accuracy.

Vacheron Constantin Malte Skeletonised caseback
The caseback view of a skeletonised Vacheron Constantin Malte Tourbillon
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Changing of the guard

At the turn of the millennium, Richard Mille established his eponymous brand, with the support of APRP, Audemars Piguet’s part-owned complications hothouse. Mille’s watches were the first since Lépine to do away with baseplates and mainplates almost entirely, and pioneered the idea of constructing a movement that was skeletonised by default, designing a framework of bridges that would just about hold everything together with the minimum metal. The creation of movements that are skeletons from their very inception is not just a technical breakthrough, but the biggest shift in watch design in decades.

Describing the thinking behind his groundbreaking approach, Richard Mille said, “In the first place it is my passion for racing cars and aircrafts that guided this approach. I am totally fascinated by what is under the hood, and seeing how everything works; this was also why from the very beginning I used open worked movement designs. Also, today, nearly everyone is – consciously or unconsciously – technically orientated.” On the question of his influence he agreed that “perhaps you could say that I took the ‘fear’ or prudery out of the naked movement issue. Now, everyone feels free to try this design ethic.”

Richard Mille RM035
The Richard Mille RM035
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Once the industry realised that machining technology had reached the point where it could cut out the middleman in the skeletonisation process, this school grew and grew. The most devoted practitioners are, as you would expect, avant-garde independent watch brands, from Angelus to Manufacture Royale, Armin Strom to Roger Dubuis, but it has permeated much further.

Angelus U21 Tourbillon in carbon and gold
Angelus U21 Tourbillon in carbon and gold
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We see it at Graff, whose faceted designs are like wireframe models of enormous gemstones, and at Ulysse Nardin, where the Executive range glories in a brutal rectangular framework. It has become the de facto design language for a fashion house looking to enter the world of fine watchmaking, be it Louis Vuitton’s first Poincon de Geneve-certified tourbillon, Chanel’s elegant Camellia or Ralph Lauren’s Automotive Skeleton. Even Raymond Weil, not known for being at the forefront of trends, went down the wide open route with its limited-run tourbillon from 2016.

Richard Mille movement under construction
A Richard Mille movement under construction
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The opening up of movements, this grand doing away with of dials, has trickled down to mainstream sports watch manufacturers too, and for that we have Jean-Claude Biver to thank (as so often with a modern trend). Hublot launched its first openworked piece in 2009, and as first TAG Heuer and now Zenith have found themselves in need of a shot in the arm, dropping the dial was directive number one. It’s the identifying trait of the Carrera Heuer 01, and looks set to be the underlying theme as Zenith braces itself for 20,000 volts to the temples - recently, a new set of openworked El Primeros were released, softening the ground for the Defy Lab. And it’s not just the LVMH club - when Bell & Ross wanted a new look, guess what: no dial on the BR-01.

But how was this to affect the brands for whom skeletonisation was traditionally their preserve? When it was an artisan handcraft, it was restricted to those at the upper echelons - with more affordable watches flaunting their synthetic rubies for all to see, what then?

A new style

The reaction from more traditional watch brands, or perhaps more accurately, watch brands whose designs are too deeply entrenched to abruptly pivot to a Mille-light style of futuristic openworking, has been the emergence of a less extreme style of modern skeleton watchmaking. One by one, manufacture brands have dropped the engraving and hand- polishing in favour of black and grey anodised bridges, relying on the interplay of grained, brushed and matte textures to provide the fireworks: take a look at Audemars Piguet’s Royal Oak skeleton or the Girard-Perregaux Laureato to see what I mean.

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Audemars Piguet Royal Oak Openworked in rose gold
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In some instances, this new skeleton style has been used to great effect in conjunction with existing design codes - the best example being Cartier’s skeletonised Roman numerals, or the ultra-thin skeleton pieces from Bulgari or Piaget. Today, few brands cater to that traditional ideal of a hand-engraved skeletonised watch. And the truth is hardly anybody does it the old-fashioned way any more: it’s just not logical to take a sawblade to full-sized bridges when machines can get you 90 per cent of the way with less wastage. Both Vacheron Constantin and Jaeger-LeCoultre confirmed that even though the appearances remain traditional, technology has had an effect. Stephane Belmont at Jaeger-LeCoultre said that “since 2008, we have been re-designing movements for skeletonisation in the lab, which lets us be more precise and reliable. But we still make prototypes by hand, cutting the bridges like we used to.”

Vacheron Constantin probably has the largest number of separate skeletonised references on its books - as befits its role in introducing the technique to wristwatches. It will evaluate any new movement’s potential for skeletonisation, and is rare even among haute de gamme brands in having the in-house manpower to do all the engraving and finishing itself. Yet even here, machines get the process started before handing over to the artisans.

Vacheron Constantin skeleton
A fully skeletonised Vacheron Constantin mainplate
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The sole exception seems to be Patek Philippe: Philip Barat, head of watch development, told QP that “we start with the whole bridge machined in our workshops, we then wire cut the excess. The hand finishing steps are mainly made in our workshops; some may be done by independent specialist artisans. It takes three times longer for the chamfering of the skeletonised parts than for the engraving, and it takes an additional 5 months compared with the same movement type (e.g. the ultra-thin self-winding calibre 240) so in total it takes about 14 months.”

The likes of Patek Philippe and Vacheron Constantin - Glashutte Original is another - all emphasised their commitment to the traditional look of a skeletonised watch, avowing that the very finest hand finishing is incompatible with the newer, more industrial style pieces.

Stephane Belmont points to the democratising effect of technology as reducing the popularity of traditionally styled skeleton watches, saying, “there are a lot of very simple movements out there, not finished well. People get a bit confused, like with tourbillons; they used to be exclusive but when you see more affordable ones come out, with poor levels of finishing and reliability, that confuses things.”

Jaeger-LeCoultre openworked pocket watch
An openworked Jaeger-LeCoultre pocket watch
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Jaeger-LeCoultre still makes between 100 and 200 skeleton watches per year, and while he readily concedes that the Richard Mille effect has been responsible for a shift towards what he describes as “something more masculine, more powerful”, there is no sign that the brand is likely to follow suit soon.

As ever in watchmaking, there will always be a place for the traditional - even if technology is assisting behind the scenes. But increasingly if you are looking for a definition of the modern wristwatch, it does not include a dial.