
Jaeger-LeCoultre expands its Master Ultra Thin Moon collection with a new interpretation that celebrates watchmaking elegance in its purest form. Dressed in a new 36 mm case in 18-carat (750/1000) pink gold, this creation pairs the warmth of precious metal with the restraint of a silver sunray dial. Beyond its refined looks, it carries on a tradition dear to the Manufacture in Le Sentier: watchmaking in which slender proportions meet mastery of mechanical complications. With its moon phase and date display, driven by the automatic calibre 925, this new Master Ultra Thin Moon embodies a timeless vision of horological luxury.
On this page
- The Master Ultra Thin collection, the art of discretion
- A pink gold case with refined proportions
- A silver dial set to the rhythm of the moon phases
- Calibre 925, mechanics serving elegance
- A black alligator strap to underline the contrast
- A timeless vision of fine watchmaking
- Technical specifications, Jaeger-LeCoultre Master Ultra Thin Moon
- Frequently asked questions
The Master Ultra Thin collection, the art of discretion
Elegance does not necessarily lie in showing off. Since its beginnings, the Master Ultra Thin collection has championed a vision of watchmaking in which pure lines, slim cases and balanced dials take centre stage.
This philosophy is rooted in the history of Jaeger-LeCoultre, whose first ultra-thin creations date back to the early 20th century. Over the decades, the Manufacture has built up an expertise that allows it to combine mastery of volumes, mechanical sophistication and aesthetic research.
Based in Le Sentier, in the heart of the Swiss Vallée de Joux, the house carries on this heritage in its integrated Manufacture, where movements are designed, made and assembled. The Master Ultra Thin collection expresses this continuity with watches whose apparent simplicity rests on genuine design and execution work.
The new Master Ultra Thin Moon fits squarely within this approach. Its 36 mm case refreshes the collection’s proportions and gives it a delicate presence, while the pink gold adds a precious, warm dimension to this classic composition.
A pink gold case with refined proportions

Crafted in 18-carat (750/1000) pink gold, the 36 mm case is one of the major developments of this new reference. Its polished surfaces catch the light and reveal the nuances of the metal, whose warm reflections play against the cooler tone of the silver dial.
At a contained 9.3 mm thick, the watch keeps a balanced silhouette, true to the spirit of the collection. The long curved lugs extend the case profile harmoniously and follow the curve of the wrist. The whole favours measured elegance, where every line contributes to the overall balance.
The gold-toned hour markers echo the shade of the pink gold, as do the faceted hands. Their finish combines one satin-brushed side with one polished side, creating subtle plays of light depending on the viewing angle. The trapezoid markers answer the geometry of the Dauphine hands, in a composition where precise shapes contribute as much to the aesthetics as to legibility.
This attention to detail illustrates Jaeger-LeCoultre’s approach: a watch is not defined by its precious materials alone, but by the way design, proportions and finishing bring them to life.
A silver dial set to the rhythm of the moon phases
The silver sunray dial offers a delicate contrast with the pink gold case. Its texture catches the light and shifts its reflections with every movement of the wrist, while its light tone ensures the indications can be read at a glance.
The layout is built on symmetry. The hours and minutes sit in a clean arrangement punctuated by gold-toned markers. At 6 o’clock, a subdial combines two indications: the date and the moon phases. This grouping preserves the balance of the dial while giving the complication a central role in the watch’s identity.
In the lower part of the dial, the moon stands out against a deep blue starry sky. Around this celestial display, the date numerals are printed in black, providing a functional contrast with the silver background.
The moon phases thus bring a poetic touch to this creation. They are a reminder that watchmaking is not limited to measuring hours: it can also depict natural cycles and the steady motion of the heavens. At Jaeger-LeCoultre, this complication fits into an architecture that favours legibility and restraint.
Calibre 925, mechanics serving elegance

Beneath its classic looks, the Master Ultra Thin Moon houses the Jaeger-LeCoultre automatic calibre 925. Designed, made and assembled at the Manufacture in Le Sentier, this movement is one of the pillars of the collection.
Regularly updated as technology has advanced, it offers a 70-hour power reserve. This autonomy keeps the watch ready to wear for longer, while meeting the demands of daily use.
The movement drives the hours, minutes and seconds, along with the date and moon phase displays. It thus combines the essential time-telling functions with a traditional astronomical complication, in an architecture designed to keep the whole slim.
The transparent sapphire caseback reveals the calibre’s finishing. Côtes de Genève structure the surfaces, while bevelled bridges and blued screws show the care given to every detail. The openworked rotor in 22-carat (916/1000) pink gold continues the aesthetic dialogue with the case, creating continuity between the exterior and the mechanism.
This attention to the movement recalls an essential trait of fine watchmaking: beauty is not limited to what you see at first glance. It extends into the mechanical components that the transparent caseback invites you to observe.
A black alligator strap to underline the contrast
The new Master Ultra Thin Moon is fitted with a black alligator strap, fastened with a pin buckle in 18-carat (750/1000) pink gold. The black adds a sober note that highlights the warm tones of the case and the brightness of the dial.
The strap is interchangeable, making it easy to refresh the watch’s look and adapt it to different occasions. This versatility matches the purpose of the collection: offering an elegance that is not reserved for exceptional circumstances, but can accompany the important moments of everyday life.
Water resistance of 5 bar completes the features of this dress watch, designed first and foremost around the finesse of its design, its refined indications and its mechanical movement.
A timeless vision of fine watchmaking
With this new Master Ultra Thin Moon, Jaeger-LeCoultre evolves a recognised aesthetic signature by giving it a new size and a warmer expression. The 36 mm pink gold case, the silver sunray dial and the moon phase display form a whole in which every detail falls naturally into place.
Calibre 925 and its 70-hour power reserve provide the mechanical substance of this creation, while the finishing visible through the sapphire caseback extends the pleasure of discovery.
Reference Q1242521 thus illustrates a vision of horological elegance based on balance rather than ostentation. A watch that is precious in its materials, sophisticated in its mechanics and timeless in the rightness of its proportions.
Technical specifications, Jaeger-LeCoultre Master Ultra Thin Moon

| Reference | Q1242521 |
|---|---|
| Case | 18-carat (750/1000) pink gold, polished surfaces |
| Dimensions | 36 mm in diameter, 9.3 mm thick |
| Dial | silver sunray, gold-toned markers and faceted hands |
| Functions | hours, minutes, seconds, date and moon phases |
| Movement | Jaeger-LeCoultre automatic calibre 925 |
| Power reserve | 70 hours |
| Caseback | transparent sapphire crystal revealing the movement |
| Movement finishing | Côtes de Genève, bevelled bridges, blued screws and openworked rotor in 22-carat (916/1000) pink gold |
| Water resistance | 5 bar |
| Strap | black alligator, interchangeable, with 18-carat (750/1000) pink gold pin buckle |
Frequently asked questions
The Master Ultra Thin Moon gets a new 36 mm case in 18-carat (750/1000) pink gold, paired with a silver sunray dial. This reference Q1242521 refreshes the collection’s proportions with a thickness of 9.3 mm.
It is driven by the Jaeger-LeCoultre automatic calibre 925, designed and made at the Manufacture in Le Sentier. It offers a 70-hour power reserve and displays the hours, minutes, seconds, date and moon phases.
A subdial at 6 o’clock combines both indications: the moon stands out against a deep blue starry sky, surrounded by date numerals printed in black.
Yes, the sapphire caseback reveals calibre 925, decorated with Côtes de Genève, bevelled bridges and blued screws, with an openworked rotor in 22-carat (916/1000) pink gold.
It comes on an interchangeable black alligator strap with an 18-carat (750/1000) pink gold pin buckle. The watch is water resistant to 5 bar.



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