Jaeger-LeCoultre
Jaeger-LeCoultre Master Ultra Thin Réserve de Marche Q1378420
The Jaeger-LeCoultre Master Ultra Thin Réserve de Marche (reference Q1378420) is a 39 mm stainless steel watch with a silver dial. It runs on the automatic caliber 938 and is water resistant to 50 m.
Specifications
Case
- Reference
- Q1378420
- Collection
- Master Ultra Thin
- Case size
- 39 mm
- Case material
- Stainless steel
- Case shape
- Round
- Crystal
- Sapphire
- Water resistance
- 50 m
- Bracelet / strap
- Alligator leather strap
Dial and bezel
- Dial
- Silver
Movement
- Movement
- Automatic
- Caliber
- 938
- Frequency
- 28,800 vph
- Functions
- Power reserve indicator, Date
Production
- Production
- Current
How it compares within the Master Ultra Thin family
Side by side with other references in the same collection, from the catalog.
| Reference | Size | Material | Dial | Caliber | Years |
|---|---|---|---|---|---|
| Q1378420 (This watch) | 39 mm | Stainless steel | Silver | 938 | — |
| Q1218420 | 39 mm | Stainless steel | Silver sunburst | 896/1 | — |
| Q1238420 | 39 mm | Stainless steel | Silver sunburst | 899/1 | — |
| Q1308470 | 39 mm | Stainless steel | Black | — | — |
| Q1358420 | 40 mm | Stainless steel | Silver | — | — |
| Q1362520 | 39 mm | 18k pink gold | Eggshell | 925/1 | — |
| Q1368420 | 39 mm | Stainless steel | Silver sunburst | 925/1 | 2015– |
| Q1368470 | 39 mm | Stainless steel | Black | 925/1 | — |
| Q1368480 | 39 mm | Stainless steel | Blue | 925/1 | — |
About the Master Ultra Thin family
Master Ultra Thin is Jaeger-LeCoultre's line of very slim dress watches, drawing on the manufacture's long history of thin movements. It includes time-only models, moon phases, perpetual calendars and tourbillons in round, classic cases.
The catalog includes references with calibers such as 896/1, 899/1 and the moon-phase 925/1, in steel, pink gold, red gold and platinum. Dealers identify the function and size from the reference and check the strap, buckle and papers.
Quick answers
- What size is the Jaeger-LeCoultre Master Ultra Thin Réserve de Marche Q1378420?
- The Jaeger-LeCoultre Master Ultra Thin Réserve de Marche Q1378420 has a 39 mm case.
- What movement does the Jaeger-LeCoultre Master Ultra Thin Réserve de Marche Q1378420 use?
- It uses the automatic caliber 938.
- How water resistant is the Jaeger-LeCoultre Master Ultra Thin Réserve de Marche Q1378420?
- It is water resistant to 50 metres.
- Is the Jaeger-LeCoultre Master Ultra Thin Réserve de Marche Q1378420 still in production?
- Yes, it is a current reference.
- What is the Jaeger-LeCoultre Master Ultra Thin Réserve de Marche Q1378420 made of?
- The case is stainless steel. Bracelet or strap: Alligator leather strap.
Catalog facts checked September 2026.