First introduced in 2018 as an experimental, one-off piece, the Piaget Altiplano Ultimate Concept – pictured above – made it into full production last year, once again making Piaget the proud makers of the thinnest mechanical watch in the world. How thin? Two millimetres. Thinner than a coin – thinner than a couple of credit cards, even. To fit an entire watch movement inside a case that size, and to have it run, reliably, for 40 hours, is one of the landmark achievements in modern watchmaking, and the latest triumph in a hotly contested decade of ever-decreasing thinness.

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Despite recent advances, however, making watches really thin isn’t anything new. Between 1764 and 1765, Mr Jean-Antoine Lépine was experimenting with how to make pocket watches less substantial, which led to him creating what we would recognise as the modern mechanical movement. Before that, large, drum-shaped movements were the order of the day.

Later, it became a question of style as well as mechanical improvement. Legendary dandy Mr Beau Brummell was one of the first to champion the idea that thinner was better in the style stakes. A big fan of clothing that fitted more closely, Mr Brummell’s streamlined style required a slimmer watch, which could be slipped into one’s pocket without ruining the lining of one’s outfit.

The next real breakthrough came in 1903, when Parisian watchmaker Mr Edmond Jaeger invented the Calibre 145 – a movement that was just 1.38mm thick. He challenged Swiss watchmakers to develop and produce his invention. Mr Jacques-David LeCoultre took up the gauntlet and Jaeger-LeCoultre became the first brand to be associated with ultra-thin watches. This is the same calibre that powered the original inspiration for the Jaeger-LeCoultre Kingsman Master Ultra Thin Knife.

Audemars Piguet, already famous for its svelte pocket watches, toppled Jaeger-LeCoultre’s crown in 1921 with a movement that slipped in at 1.32mm. It took another 36 years for the next record breaker to appear, when in 1957 Piaget launched the 9P. The movement was just 2mm thick and allowed the brand to produce thinner watches than its competitors, often with incredible stone dials that were themselves just 0.7mm in thickness.

Another mechanical pioneer in this field, though one who is lesser known and not as successful, was Mr Jean Lassale. In 1976, Mr Lassale turned up at Basel Fair with two calibres, both in a 3mm cases – the hand-wound Calibre 1200 at 1.2mm and the 2000, an automatic at 2.08mm. All the moving components were on one side only, with the barrel, mainspring and ratchet wheel free floating and guided by ball bearings rather than a traditional pivot. There were no bridges, apart from the pallet and balance, and everything else was supported on a single plate.

These movements weren’t just so thin as to affect their timekeeping; taking the back off the watch would irrevocably damage the movement, so you’d have to replace the whole thing instead of servicing it. Mr Lassale also never managed to work out how to stop the crystal from snapping if you had the strap a bit too tight. When Mr Lassale failed to make a success of his invention, Mr Claude Burkhalter, founder of Nouvelle Lemania – the same movement maker to collaborate with Omega on the legendary Calibre 861 that went to the moon on the wrists of Messrs Neil Armstrong and Buzz Aldrin – purchased the patents along with the movements. The former he sold to Piaget.

After this, the world of ultra-thin was dominated by the quartz brands. The rise of the battery meant you didn’t need so much stuff under the bonnet, so the watches could be even thinner than those that required gear trains and mainsprings. The pinnacle of this period was the Concord Delirium, launched in 1979 and just 1.98mm thin. Audemars Piguet stuck its head above the parapet once again in 1986, taking the world record for the thinnest, and first, automatic tourbillon; a feat it achieved by ditching the rotor and using a winding hammer instead.

In the early 2000s, getting things super thin took a back seat in favour of ever-more elaborate tourbillon constructions and seeing who could clock up the biggest case diameter. Then in 2013, Piaget’s 900P arrived and the competition was back on. Since then, records have changed hands between Piaget, Bulgari and Jaeger-LeCoultre with each adopting different technical approaches to the problem.

For brands competing in this field, thinness is a complication; as difficult to master as a perpetual calendar. Firstly, the necessary changes to movement architecture pose risks that need to be mitigated. For example Jaeger-LeCoultre’s Calibre 849, found in the Kingsman “knife” dress watch, has a hanging barrel – a mainspring with no upper bridge only running on one pivot attached to the mainplate. You lose valuable depth having it like this but it’s less stable. According to Mr Stéphane Belmont of Jaeger-LeCoultre, the Kingsman watch is as thin as a watch can get while retaining a traditional dial and case construction: the whole watch measures 4.25mm. Which puts the achievement of the Piaget back into context.

Many thin movements use micro rotors, which are smaller than full-sized automatic rotors, and have the advantage that you can set them into the body of the movement rather than adding them to the back, removing a lot of thickness, but the loss of weight on the rotor itself means it doesn’t swing as well – so it’s harder for it to wind the watch – and a lot of adjustment is needed to make sure performance isn’t affected. Something which Bulgari had to contend with when it unveiled the world’s thinnest chronograph in 2019.

“We’ve spent years developing this,” says Mr Fabrizio Buonamassa Stigliani, the brand’s head of watch design. “It was hard enough getting this level of thinness with just minutes and seconds to worry about; with a chronograph it’s even worse. A chronograph needs torque, which is why you can’t use a micro rotor.”

The eventual solution was a peripheral rotor sitting snugly around the edge of the movement, in platinum to give it the necessary weight. “It also had to have a slightly larger 42mm case because, in order to keep the thinness, the bracelet passes inside the case,” he adds.

When you get to the levels of thinness witnessed in Piaget’s latest creation, the Altiplano Ultimate Concept, the challenges really pile up. In addition to all of the above issues, every fraction of a millimetre saved brings new hurdles.

“This watch has no fewer than five patents. We had to completely rethink the construction of the watch,” says Mr Quentin Herbert, head of watchmaking at Piaget. “With components as thin as a hair, we had to innovate to find a high-strength material to make this watch. Gold would be too malleable for such extreme thinness. So, the case had to be made from a new, cobalt-based alloy that is highly resistant, 2.3 times stronger than gold, but much harder to machine. Other parts were entirely resized. During the two years between prototype and the watch we sell today, there were multiple challenges, including ensuring a sustainable assembly and having the ability to maintain the watch for its lifespan.” There’s more: the sapphire crystal atop the watch is just 0.2mm thick yet still strong enough to function on a series-produced watch. Take a piece of regular A4 paper, fold it in half and that’s what you’re looking at.

Technological advancements have made this possible, not only in machining solutions, but, as Mr Herbert points out, also in terms of innovative processes and assembly. There is also something freeing about wearing a watch that is so thin and light that you don’t even notice it on your wrist.

“The right thinness is in its comfort,” says Mr Herbert. “When you forget your watch, then your watch becomes the perfect companion to life’s precious moments.” Have we reached peak thinness? Not according to Mr Herbert.  “Six years ago, we had no idea how to reach 2mm thinness for a watch. Today it’s a reality,” he says. “So, I think that, yes, in six years, we could find other nano-solutions to get to a new level in extreme ultra-thinness.”

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