Jaeger-LeCoultre Master Control Chronometre: The 1,000-Hour Test Behind the New Collection
Jaeger-LeCoultre stacks its own 1,000 Hours Control on top of COSC certification for the Master Control Chronometre line. A working dealer's read on what the High Precision Guarantee actually tests, the Q4158120 Date and Q4178180 Perpetual Calendar references, and what it means for a pre-owned buyer.