Forty years of the Patek Philippe Caliber 240

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Reminiscing the year 1977, 40 years ago. This may sound like the distant past. Some of us might not have been born yet then, but for those who have (or the history buffs), we consider those momentous events in the year with fondness. Who could forget cinema-goers queuing for hours to catch the first Star Wars movie, or Tony Manero grooving to the songs in Saturday Night Fever. It was also the year of “consumer technology”. Apple Computer was incorporated by Steve Jobs and Steve Wozniak and sold their first fully assembled personal computer. And of course, for the watch nerds, the birth of the Patek Philippe Caliber 240, ultra-thin automatic movement.

In essence 1977 was the year in the middle of the horology crisis, during which cheap quartz timepieces threatened the very foundations of the Swiss watchmaking industry. However under these circumstances, Patek Philippe saw the need to courageously invest in a new mechanical movement and build up fresh momentum for the more than 500-year-old heritage of genuine watchmaking artistry.

Patek Philippe Caliber 240: slimming the automatic movement

The legendary Patek Philippe Caliber 240 was born out of the demand to have a self-winding, ultra-thin movement. It’s world debut took place beneath the slender gold hour and minute hands of the uniquely-shaped Golden Ellipse 3738 men’s wristwatch. This was Patek Phillipe’s elegant strategy to safeguard the future of the manufacture. The self-winding movement was meant to outperform its quartz counterparts, not with respect to rate accuracy and not to compete in the low-end price range. But in categories where Patek has the undisputed superiority, such as beauty, reliability, longevity, intrinsic value, and elegance.


The Caliber 240 as seen in the Patek Philippe Ref. 6006. One of the latest outings for the venerable C.240, introduced this year in Baselworld 2017.


What sets the original Caliber 240 apart from the rest is that it is not thicker than a flat manually wound movement. The base Caliber 240 achieves a height of only 2.53mm. The height is even smaller than the Patek basic workhorse manual wind caliber 215, which calls in at 2.55mm.

The original Caliber 240 featured a very small, off-center winding rotor that was completely recessed in the plate plane. The engineers in technical director Gérard Berret’s team knew that a small planetary rotor could not build up the same winding power as a large and massive central rotor so they increased the mass of the off-center rotor by making it in 22K gold. A unidirectional winding concept was implemented to reduced friction losses because no reversing gear was required. Overall efficiency from the winder and the spring barrel to the escapement was further improved with a totally new going train featuring an optimized toothing geometry and polished teeth. Last but not least, the frequency of 3 Hz (21,600 vph) reduced the energy consumption of the movement by more than 20% in comparison with conventional 4 Hz movements.

The variations of the Caliber 240 and the Patek Philippe hall of fame which are so powered.

Click here to view the image in original size.


The caliber 240 as an innovation driver

Over the years, the Caliber 240 has been optimized in many respects but still retains its original DNA. For instance, it still beats with a frequency of 21,600 semi-oscillations per hour but now with a patented Spiromax® balance spring in Silinvar® manufactured by Patek Philippe that enables it to achieve even better rate accuracy. The tooth profiles of the going train were further optimized to reduce wear, improve accuracy, increase the power reserve and boost long-term reliability.


Patek Caliber 240 HU. HU stands for Heure Universelle, meaning universal time. Here the base 240 is enhanced with the world time function and is seen in the Ref. 5230 World Time.


In the Ref. 5550 Perpetual Calendar “Patek Philippe Advanced Research“, the caliber 240 movement delivered another innovation thrust in 2011: The Spiromax® balance spring and the Pulsomax® escapement (lever and escape wheel in Silinvar®) paired with the GyromaxSi® balance in Silinvar® and 22K gold constitute the Oscillomax® ensemble attains previously unmatched results in rate accuracy and autonomy – more than 70 hours as opposed to at most 48 hours in the normal version.

Over the years, the Caliber 240 remains the preferred choice of base for the manufacture’s complications in its range of slim watches. Our Infographic below shows the key watches.




In 1985, it stood out in the 240 Q (Quantième Perpétuel) version with a height of only 3.75 mm in the legendary ultra-thin Ref. 3940 Perpetual Calendar, the first Patek Philippe self-winding wrist watch with a perpetual calendar and moon phase indicator. The 3940 remains as a grail for many Patek Philippe collectors worldwide since its inception thanks to its beautiful dial proportions and its skillfully assembled complication.

The Calatrava Ref. 5015 (1994 in the Infographic above) that dates back to 1994 achieved a milestone in the history of the manufacture. With moon phases and a power-reserve indicator, it was the first model of the “useful complications” collection, using the 240 PS (Petite Seconde) at 3.98mm.

The 240 HU (Heure Universelle) that powers the classic World Time Ref. 5110 indicating 24 time zones on the timepiece (as shown in year 2000 in the Infographic above) sits at 3.88mm thick, which is a feat for such complications as it includes the quick-set local time feature, which rotates the outer dial with the names of the cities and the 24-hour ring in anti-clockwise direction. It also jumps the hour hand ahead in one hour increments. Read more about the World Time timepiece here from our hands-on review on its successor, the Ref. 5230 World Time.

The 240 LU CL C (Phase de lune Ciel Calendar) housed in the Celestial 5102 (as shown in year 2002 above) and the 6102R is the thickest variation of the Caliber 240. Yet it is only a mere 6.81mm thick, and the timepiece still sits compact and flat on the wrist.

Today in year 2017 the Caliber 240 celebrates its 40th anniversary with three new models presented at Baselworld 2017, that continues to emphasize the versatility of the movement and of the manufacture. The debut models are the artistically skeletonized and engraved Calatrava Ref. 5180/1 “Squelette” in rose gold, the quirky and face-lifted Calatrava Ref. 6006 as inspired by the original Ref. 5000 featuring a seconds sub-dial between 4 and 5 o’clock, as well as the ladies’ haute joaillerie Ref. 4899/900, set with white Top Wesselton diamonds and rose sapphires of different color intensities.

We continue to admire Patek Philippe’s commitment to the ultra-thin automatic movement, and hope to see further advances to the Caliber 240 movement in the future.

The Patek Philippe Caliber 240 base movement specifications

Caliber 240 – Self-winding movements
Technical Data
Ultra-thin mechanical self-winding movement
Caliber 240
22K gold off-center mini-rotor
Diameter: 27.5 mm
Height: 2.53 mm
Jewels: 27
Bridges: 6
Parts: 161
Power reserve: Min. 48 hours
Balance: Gyromax®
Vibrations/hour: 21 600 (3 Hz)
Balance spring: Spiromax®
Hallmark: Patek Philippe Seal
Patent: CH 595 653


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1 Comment

  1. Tony Gedalovitch on

    Don’t forget this also means that the ref. 3738 is the same age, Patel’s longest running production model.