2025 Jaeger-LeCoultre Master Ultra Thin Réserve de Marche

Jaeger-LeCoultre Master Ultra Thin Réserve de Marche 39mm — Ref. Q1378421

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The Master Ultra Thin collection is where Jaeger-LeCoultre shows what it can do when thinness is the entire design brief — and the Réserve de Marche proves that "ultra thin" doesn't have to mean "stripped down." This 39mm case manages to house an in-house automatic caliber with a date display, small seconds, and a power reserve indicator while staying slim enough to slide under any cuff without a fight. The updated Caliber 938 brings a silicon escapement to the equation, which does two things that matter: it improves long-term accuracy by resisting magnetic fields, and it extends the power reserve to a full 70 hours — nearly three days off the wrist from a movement this thin. The silver-grey sunray dial catches light in a way that shifts between warm silver and cool steel depending on the angle, with dauphine hands and elongated stick markers that keep the layout clean despite three complications sharing the dial. The power reserve indicator sits opposite the small seconds, balanced around a date window at 3 o'clock, and the whole arrangement reads as effortless rather than crowded. Through the sapphire exhibition caseback, the finishing on the 938 is on full display — this is a manufacture movement from a brand that's been building them since 1833, and it looks the part. At 39mm on a black alligator strap with a double-folding clasp, this is the kind of watch that makes everything else on your wrist feel loud.

Specifications

• Model: Master Ultra Thin Réserve de Marche
• Reference: Q1378421
• Caliber: Jaeger-LeCoultre 938 — 41 jewels, 28,800 vph (4 Hz), in-house manufacture, automatic, silicon escapement
• Case Material: Stainless Steel
• Case Diameter: 39mm
• Case Thickness: 8.95mm
• Lug Width: 21mm
• Bezel: Stainless steel, fixed
• Crystal: Sapphire with anti-reflective treatment
• Caseback: Sapphire crystal exhibition
• Dial: Silver-grey sunray-brushed, dauphine hands, elongated stick hour markers
• Strap: Black alligator leather with stainless steel double-folding clasp
• Movement: Automatic
• Components: 273
• Power Reserve: 70 hours
• Water Resistance: 50 meters (5 bar)
• Functions: Hours, minutes, small seconds, date (3 o'clock), power reserve indicator

Condition Report

• Case: 10/10
• Bezel: 10/10
• Crystal: 10/10
• Dial/Hands: 10/10
• Strap: 10/10
• Clasp: 10/10
• Caseback: 10/10

Polishing Status: Unpolished

Delivery Contents

• Complete set — box, papers, warranty card, manuals

Please refer to photos for full contents.

Service & Authenticity

• Timegrapher: 336 amplitude
• Service History: No known service history
• Warranty: Active — card dated March 2025, base coverage through March 2027, extendable to March 2033 via JLC Care program

Shipping & Legal

• Based in: Cullman, AL
• We serve buyers in Nashville, Atlanta, and Memphis — insured shipping or in-person meetup available.
• Shipping: Fully insured overnight with tracking provided
• Shipping within CONUS only
• Buyers are responsible for any applicable taxes and duties
• Watch is sold in accordance with United States laws and regulations

All watches are inspected by our watchmakers for condition, authenticity, and functionality before sale. Feel free to reach out via messenger with any questions.