Jaeger-LeCoultre
JLC cal 849
Swiss lever · introduced 1979
Beat rate
28,800 vph
Power reserve
43h
Jewels
20
Introduced
1979
Escapement
Swiss lever
The JLC 849 is among the thinnest mechanical movements ever produced at 1.85 mm, defining the Master Ultra Thin's 4.05 mm total case height. It sacrifices no reliability for its architecture: 43 hours of manual-wind reserve from a single barrel and 20 jewels. The appeal is entirely in its watchmaking discipline: achieving consistent timekeeping at a scale where gravity acts on components measured in microns.
Specifications
Beats per hour
28,800
Jewels
20
Power reserve
43h
Diameter
20.4mm
Height
1.85mm
Escapement
Swiss lever
Introduced
1979
Finishing
Fine
Service interval
5 years
Service cost tier
Luxury
Complications
manual wind
Known service issues
- Manual wind only; it will stop within two days if not wound, which is normal for the architecture
- The thin balance cock requires care at service; a dropped part is difficult to replace without factory access
Notable in
- JLC Master Ultra Thin 145.8.79.S
- JLC Master Ultra Thin Perpetual Q1303520
Buying advice
Practical guides for buying a watch with this caliber on the pre-owned market: