Master Ultra Thin Knife

In Context

At 40 mm it is sized to the current mainstream: 40 mm is the median across every watch measured in this catalogue. The 4.25 mm case is genuinely slim and goes under a shirt cuff without argument. The case back is open, so the movement is visible without taking the watch apart, and the sapphire crystal will resist everything short of deliberate abuse. 50 m covers rain and hand-washing comfortably; it is not a watch to swim in.

The movement is hand-wound, so winding it becomes part of the day rather than something the watch does for you. Its 35-hour reserve wants wearing most days; leave it off and it stops. At 21,600 vph the seconds hand advances 6 times a second, the slower and more audible rate of an older design.

1152520 stands on its own in this catalogue — no other reference here shares its base number. It pairs a silver matte dial with a pink gold case. It was a limited edition. Introduced in 2020.

At 1.85 mm deep, long the thinnest hand-wound movement in production, and the direct descendant of the 839 of 1975. Its 123 parts leave no room for a rotor, which is rather the point: the calibre exists so a mechanical watch can be made almost flat. A Glucydur balance and flat Nivarox hairspring regulate it, with Côtes de Genève on the bridges.

5 other watches in the library run the Jaeger-LeCoultre 849.

Jaeger-LeCoultre

Reverso à Eclipse Van Gogh Sunflowers

216279 · 26 mm

Jaeger-LeCoultre

Master Ultra Thin Pink Gold Diamond

1452507 · 34 mm

Jaeger-LeCoultre

Master Ultra Thin 1907 Boutique Edition

12935E1 · 39 mm

Jaeger-LeCoultre

Master Ultra Thin 1907 Platinum

1296520 · 39 mm