Jaeger-LeCoultre Master Ultra Thin Perpetual

The latest addition to Jaeger-LeCoultre’s Master Ultra Thin line is also the collection’s first perpetual calendar (QP, for those in the know). Elegant and pared back, it has the luxury of catching the eye while remaining resolutely understated. Welcome to the Jaeger-LeCoultre Master Ultra Thin Perpetual.

This new ultra-thin calibre therefore adopts a highly sought-after complication—one that is particularly complex to implement in such a slim profile—while presenting a complete perpetual calendar on the dial as clearly as possible.

The perpetual calendar is read via the three sub-dials. The day of the week appears at 9 o’clock, the date (definition of the date) at 3 o’clock, and the month at 6 o’clock.

The moon phases are displayed at 12 o’clock. Finally, the four digits of the year can be read in its aperture at 7 o’clock on the dial.

As for the case, the diameter will happily suit slimmer wrists, as it measures a modest 39 mm. With tapered lugs, the slender bezel gives pride of place to the dial. A key detail for an ultra-thin watch: thickness. Jaeger-LeCoultre has managed to integrate the perpetual calendar of its calibre 868 into a case just 9.2 millimetres thick. The caseback is, of course, fitted with a sapphire crystal to admire the 22-carat gold rotor segment and other movement decorations.

Setting the watch is particularly straightforward thanks to a single corrector on the side of the case, which, with one press, advances the perpetual calendar by one day. All the changes required to remain aligned with the Gregorian calendar are, of course, automatic: leap years, 28-, 30- or 31-day months—everything is “included in the package”.

Unless the Earth’s axis of rotation changes, the poles swap places, or some other whim occurs over the next 122 years, the moon phases will also remain true to reality.

In watchmaking there is a “death zone”, a time of day when it is not recommended to set your watch, at the risk of ending up needing a service from the watchmaker.

Accordingly, just above the centre of the dial, a small window gradually turns red as evening approaches. And yes, you cheeky devil—you surely don’t want to disturb the gear train already engaged in the changes that take place at midnight on the dial, do you?

The automatic movement, made up of 336 components, 46 jewels and measuring 4.72 m,m in height, delivers a 38-hour power reserve in a case water-resistant to 5 atm.

3 versions of the Master Ultra Thin Perpetual are available: