Jaeger-LeCoultre has introduced the Master Ultra Thin Moon in a new 36mm case of 18k pink gold. The Ref. Q1242521 measures 9.3mm thick, pairs a silvered sunray-brushed dial with a moon phase and date at 6 o’clock, and runs on the self-winding, in-house caliber 925 with a 70-hour power reserve. It is priced at $23,100.
The Jaeger-LeCoultre Master Ultra Thin Moon Ref. Q1242521 comes in a new 36mm, 9.3mm-thick 18k pink gold case with a silvered sunray dial, moon phase and date at 6 o'clock, and the self-winding caliber 925 with 70 hours of power reserve, priced at $23,100.
The Maison has been making ultra-thin watches since the early 1900s, and the Master Ultra Thin collection was conceived as a quintessential dress watch for the 21st century: clean lines, polished surfaces, and long, curving lugs. This new reference leans further into that heritage. Its slimmer 36mm case pays tribute to the proportions of 1950s round watches, a size that slips easily under a shirt cuff.

The Jaeger-LeCoultre Master Ultra Thin Moon in Pink Gold
The case, bezel, and curved lugs are fully polished, and the warm shine of the pink gold plays against the cool, subtly textured silvered dial. Gilt trapezoidal hour markers echo the case color, and their shape is mirrored by the faceted Dauphine hands, one side satin-brushed and the other polished, so the hands catch light differently as the wrist turns.

In my view, the dial is where this watch earns its keep. Jaeger-LeCoultre describes the layout as an exercise in symmetry and balance, and the combined moon phase and date display at 6 o’clock anchors everything. The moon sits against a deep blue, starry background, with the dates printed in black around the aperture, giving a single, legible point of color on an otherwise restrained face.

Proportion matters as much as finish on a dress watch, and at 9.3mm thick the case keeps a low profile on the wrist. It comes on a black alligator strap fitted with an 18k pink gold pin buckle, and the strap can be easily interchanged to suit the wearer, a welcome bit of versatility on a watch that otherwise speaks the formal language of the collection. Water resistance is rated at 5 bar.
Caliber 925 and the Vallée de Joux
Inside is caliber 925, designed, manufactured, and assembled at Jaeger-LeCoultre’s Manufacture-Atelier in Le Sentier. The self-winding caliber is one of the mainstays of the Maison’s collection, proven over many years and regularly updated to improve reliability and precision. Its latest versions deliver a 70-hour power reserve, so the watch can sit in a drawer over a weekend and still be running on Monday morning.

Turn the watch over and the sapphire caseback puts the finishing on full view: Côtes de Genève, beveled bridges, and blue screws, all set beneath an open-worked rotor in 22k pink gold. My favorite detail is that rotor, because it carries the warmth of the case through to the movement side, a quiet touch most wearers will only ever show to friends.

That finishing comes from a Manufacture that counts more than 1,400 calibers and over 430 patents since 1833. The new Master Ultra Thin Moon in pink gold is priced at $23,100 and is presented on Jaeger-LeCoultre’s Master Ultra Thin Moon page, with boutique availability. It is a classic dress watch, sized like the dress watches of yesteryear, and backed by the full depth of the Vallée de Joux.
| Specification | Detail |
|---|---|
| Reference | Q1242521 |
| Case | 18k pink gold (750/1000), fully polished |
| Dimensions | 36mm diameter x 9.3mm thick |
| Caliber | Self-winding Jaeger-LeCoultre caliber 925, in-house |
| Functions | Hours, minutes, seconds, moon phase, date |
| Power reserve | 70 hours |
| Dial | Silver-colored, sunray-brushed |
| Water resistance | 5 bar |
| Strap | Black alligator, interchangeable, with 18k pink gold pin buckle |
