Jaeger-LeCoultre Master Ulra Thin Power Reserve automatic silver dial leather strap 39 mm

Master Ultra Thin: The Tradition of Horological Elegance

For more than 190 years, Jaeger-LeCoultre has cultivated the art of creating timepieces where mechanical expertise is discreetly concealed behind absolute sobriety. The Master Ultra Thin collection, launched in the 1990s, embodies this quest for balance between horological innovation and pure aesthetics. It pays tribute to a long-standing tradition in the Vallée de Joux: the mastery of ultra-thin watches, which the Maison has elevated to iconic status thanks to manufacture calibres of remarkable finesse.
The reference Q1378421 is part of this lineage: a contemporary timepiece that combines timeless elegance, ideal proportions, and useful complications, while remaining faithful to the historic savoir-faire of the Grande Maison.

A Design of Timeless Elegance

The 39 mm stainless steel case impresses with its perfect balance: wide enough to assert itself on the wrist, yet slim (less than 9 mm thick) to ensure absolute discretion under a shirt cuff. Finely polished, it captures the light and emphasizes the slender, curved lugs characteristic of the Master Ultra Thin line.

The silvered dial, with its unique architecture, stands out thanks to its sunray finish, which plays with the light and brings to life the Dauphine hands with polished and satin-finished surfaces, elongated applied indexes, and delicate minute markers. Three indications are integrated with great harmony:

• at 10 o’clock, the power reserve indicator highlights the movement’s generous autonomy;
• at 6 o’clock, the small seconds subdial brings subtle animation to the display;
• at 2 o’clock, the date window adds a practical and functional touch.

Every element has been designed to achieve perfect visual balance, in keeping with the spirit of the collection.

The Jaeger-LeCoultre Calibre 938: A Concentration of Expertise

The Master Ultra Thin Power Reserve Q1378421 houses the automatic Calibre 938, a manufacture movement entirely conceived, decorated, and assembled within the Manufacture in the Vallée de Joux.

• Movement thickness: only 4.9 mm, an achievement in miniaturization that does not compromise robustness.
• Power reserve: 70 hours of autonomy, made possible by an optimized barrel and the use of a silicon escapement.
• Precision: a frequency of 28,800 vibrations per hour (4 Hz).
• Complexity: 262 components, including 39 jewels.

Each movement undergoes the exclusive in-house “1,000 Hours Control” protocol, a stringent quality certification that tests the watch in all positions and real-life conditions, guaranteeing exemplary reliability.

Through the sapphire crystal caseback, the wearer can admire the beauty of the movement: the openworked oscillating weight decorated with Côtes de Genève and the traditional finishes, reflecting the artisanal excellence of Jaeger-LeCoultre.

A Timepiece Designed for Everyday Elegance

The Master Ultra Thin Power Reserve is not merely an exercise in horological style: it is a functional and modern watch, designed to adapt to every situation. With a water resistance of 5 bar (50 meters), its comfort on the wrist, and its universal elegance, it embodies the quintessential dress watch, equally at ease in the office or at an evening event.

The hand-stitched alligator strap, paired with a stainless steel folding clasp, completes the refinement of the piece. With a 21 mm lug width, it ensures comfort and balance, while allowing personalization for those who wish to alternate with other leather straps.