• New-Generation Jaeger-LeCoultre Calibre 938 provides a 70-Hour Power Reserve
  • A Sophisticated Aesthetic Update and a Gradient Blue Dial

The Master Ultra Thin collection epitomises Jaeger-LeCoultre’s philosophy of watchmaking, uniting timeless beauty with mechanical virtuosity to create the quintessential dress watch for the modern aesthete. In 2023, the collection is enriched by a new interpretation of the Master Ultra Thin Power Reserve, featuring a subtly modernised case and dial design, a new gradient midnight blue sunray dial, and a significantly increased power reserve.

Jaeger-LeCoultre Calibre 938 Revised to Provide a 70-Hour Power Reserve

In line with La Grande Maison’s pursuit of timekeeping precision, together with added utility for the user, the Manufacture constantly improves its in-house calibres in line with advancing technology. Calibre 938 has been significantly revised to power a new generation of timepieces. Most notably, the power reserve has been increased to 70 hours – long enough to leave the watch aside for an entire weekend and wear it again on Monday with no need to rewind it or reset the time.

This significant gain in power reserve has been achieved without adding to the size of the calibre, which remains 4.9mm thick. The mainspring barrel was redesigned, some key components are now made of silicon, which makes energy transmission smoother by reducing friction of the moving parts, and other minor changes have been made to bring greater reliability.

The power reserve function is a signature complication of Jaeger-LeCoultre, pioneered by the Manufacture in 1948 with the introduction of Calibre 481. The Powermatic, recognised by its distinctive red-and-white indicator, was the world’s first self-winding timepiece with a power reserve gauge and quickly became a key model for the Manufacture in the early 1950s. The Master Ultra Thin Power Reserve is equally recognisable, with the distinctive design of the power reserve display complemented by date and small seconds indicators – the three complications bearing witness to the complexity of the calibre and the technical savoir-faire of Jaeger-LeCoultre’s watchmakers.

A Sophisticated Aesthetic Update and a Beautiful Midnight Blue Dial

While the size of the case remains the same as the preceding version of the Master Ultra Thin Power Reserve – retaining the elegant 39mm diameter and 8.95mm thickness – its design has been subtly modernised, with revised proportions and slimmer, more elongated lugs that make it even more comfortable on the wrist.

The dial architecture has also been refined. While retaining all the symmetry and balance of the earlier dial layout, larger sub-dials highlight the complications, making the date, power reserve and small seconds displays even more legible than before, while giving the dial a more integrated overall appearance. This is amplified by the newly elongated shape of the applied hour markers, and the use of a different finish (polished and satin) on each facet of the Dauphine hands, and the use of transferred golden dots to mark the minutes track. Matching the colour of the pink gold case, these elements create aesthetic harmony while contrasting dramatically with the gradient midnight blue of the sunray dial. The subtle matt texture of the sub-dials adds visual depth and richness.

Adding a final flourish, the new Master Ultra Thin Power Reserve is presented on a navy-blue alligator strap. Straps and buckles can be very easily interchanged as the wearer wishes – adding even more versatility to this sophisticated, modern timepiece.



Case: Pink Gold 750/1000 (18 carats)

Dimensions: 39 mm diameter x 8.95 mm thick

Calibre: Jaeger-LeCoultre Automatic Calibre 938

Functions: Hours, minutes, small seconds, date, power reserve indicator

Power Reserve: 70 hours

Dial: Gradient blue sunrayed

Water resistance: 5 bar

Strap: Blue alligator

Reference: Q137258J

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