Jaeger-LeCoultre Master Ultra Thin Date – Ref. Q1238421
The Jaeger-LeCoultre Master Ultra Thin Date Ref. Q1238421 is a refined embodiment of elegance and precision. Released in 2025, this 39 mm stainless steel timepiece melds classic proportions with subtle updates to the dial, delivering an elevated dress watch experience. With its ultra-thin profile, balanced aesthetics, and long power reserve, it’s designed for connoisseurs of understated luxury.
Sleek Stainless Steel Case & Slim Profile
This model features a 39 mm stainless steel case with a case thickness of just 7.889 mm, giving it an impressively slim silhouette that sits with ease under a cuff. Its round shape, polished bezel, and refined lugs preserve the classic lines of the Master collection. Water resistance is rated at 5 bar (≈ 50 meters), suitable for everyday wear in formal and semi-formal settings.
Refined Silvered Grey Sun-Rayed Dial
The silvered-grey sunburst dial of Q1238421 catches light with a subtle radiance. Hour markers have been reworked for greater length and slimmer, more elegant proportions. Dauphine hands sweep across the dial with clarity. Notably, the date display now sits at 6 o’clock, moving away from traditional 3-o’clock placement to improve symmetry — a small but significant change that enhances the watch’s balanced appearance.
Movement & Power Reserve — Calibre 899
Powering this piece is Jaeger-LeCoultre’s automatic Calibre 899, featuring hours, minutes, seconds, and date functions. It operates at 28,800 vph (4 Hz) and delivers a generous 70-hour power reserve. The movement has been subtly upgraded in recent production runs with enhancements to the barrel and possibly a silicon escapement in some versions, though the base calibre number remains unchanged.
Interchangeable Straps & Elegant Wearability
The Q1238421 comes fitted with a black alligator leather strap secured by a stainless steel double-folding buckle. The strap is interchangeable — allowing the wearer to change the look with ease. Lug width is 21 mm, measuring approximately 75 mm on the 12 o’clock side and 120 mm on the 6 o’clock side, offering a comfortable fit for various wrist sizes.
Key Technical Specifications
- Reference: Q1238421
- Case Material: Stainless Steel
- Diameter: 39 mm
- Thickness: ~7.889 mm
- Water Resistance: 5 bar / ~50 meters
- Dial: Silvered-grey sunburst, date at 6 o’clock
- Hands & Markers: Dauphine hands, elongated indices
- Movement: Calibre 899 automatic, 70-hour reserve
- Strap: Black alligator leather, stainless steel folding clasp
What Makes Q1238421 Unique
- Refined updates: The date moved to 6 o’clock and longer, more elegant indices give the watch a fresh, balanced face without departing from tradition.
- Ultra-thin precision: The ~7.9 mm thickness and Calibre 899’s strong 70-hour power reserve places this model among the more elegant yet dependable dress watches available.
- Modern classic styling: Silvered sunray dial, dauphine hands, and stainless steel combine for a look that pairs well with both formal and smart casual attire.
Conclusion
The Jaeger-LeCoultre Master Ultra Thin Date Ref. Q1238421 is a watch for those who appreciate the art of subtlety. With its elegant dialing, updated design touches, long power reserve, and slim yet substantial stainless steel case, it is a perfect choice for someone seeking a refined, versatile dress watch that is both timeless and modern.

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