Technical review of the mythical 240 Caliber from Patek Philippe

Some calibers have gone down in the history of watchmaking more than others, not only for their design, but also for their durability and reliability (we've got the El Primero by Zenith in mind).

The 240 from the Geneva-based manufacturer was introduced in the midst of the Quartz crisis in 1977 as part of the Ellipse collection, providing the case with an unrivaled level of finesse.

The thinnest self-winding caliber of its kind ever, with a daring design. The watchmaking prowess resides in its eccentric micro-rotor, which is itself housed within the caliber's thickness. The oscillating weight is made of 22K gold to compensate for the lack of inertia (compared to a central rotor), 22K gold being heavier and therefore more responsive to wrist movements.

Image of the Ellipse ref. 3738

The 240 caliber's base was used in a multitude of variations, embellished with different plates depending on the complications (perpetual calendar, world time, astronomical watch with a depiction of the starry sky as well as the moon phases...).

Variations of the 240 calibre

- 240 PS (Petite Seconde)
- 240 Q (Quantième)
- 240 PS C (Petite Seconde Calendrier)
- 240 HU (Heure Universelle)
- 240 PS IRM C LU (Petite Seconde, Indicateur de Réserve de Marche, Calendrier, Phase de Lune)
- 240 SQU (Squelette)
- 240 LU CL (Phases de Lune, Céléstial)

It was introduced in the legendary Nautilus collection in 2005 under the reference 3712 (which later evolved into reference 5712, still powered by the same caliber).

Though its design has stayed the same for nearly forty years, the Geneva watchmaker has incorporated subtle improvements to enhance its performance, especially for its power reserve. The "Advanced Research" collection is a fully integrated research and development laboratory, allowing Patek Philippe to test new materials such as Silinvar (a material derived from silicon) that significantly reduces friction.

A new version of the caliber came out in 2011 under reference 5550P, powered by the 240 Q SI caliber, which resulted in 17 patents being filed.

Image of the 5550P « Advanced Research » reference

The set including the patented components used in the 240 Q SI includes:
- Oscillomax®: Balance wheel: GyromaxSi® (in Silinvar® and 24 carat gold) - Flat balance spring: Spiromax® (in Silinvar®)
- Escapement: Pulsomax® (anchor and anchor wheel in Silinvar®)

The 240 can be regarded as a signature of Patek Philippe, whose design has proven itself through time. Now improved and still at the heart of the Patek Philippe collection, it is safe to say it has many more good days ahead.

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