Short answer
A fake Jaeger-LeCoultre 1398420 fails on four checks: the case back engraving, the movement, the reference format, and the price. Jaeger-LeCoultre reference numbers start with the letter Q. The full form is Q1398420. A seller who drops the Q, or who fits that number to a Reverso case, is describing a watch the factory did not build. Used steel JLC watches in this family sell for thousands of US dollars, not hundreds. A new-looking example at a few hundred dollars is not genuine.
What the reference number means
JLC stamps two numbers on the case back. The reference identifies the model, the case metal, and the dial variant. The serial number identifies one single watch. Both numbers must match the certificate, the warranty card, and any service record.
Counterfeits fail here first. The engraving is shallow, wide, or cut with a laser. The letters in Jaeger-LeCoultre touch. The serial on the case back does not match the serial on the paperwork.
Movement
JLC makes its own movements in Le Sentier, Switzerland. A caliber in this reference family runs at 28,800 vibrations per hour, or 4 Hz, with a power reserve near 38 hours. Bridges carry Cotes de Geneve stripes. The base plate carries perlage. The rotor is engraved with the maker name and the caliber number.
Copies use bought-in movements. Signs to look for: a blank rotor, no jewel count, uneven striping, and a rotor that rattles when the watch is turned over. A quartz copy ticks once per second. A real 4 Hz movement advances the seconds hand eight times per second.
Dial and case
- Applied indices sit flat and reflect light in one plane. Painted indices look dull.
- Hands are heat-blued steel. Painted hands show a flat blue coat.
- Sapphire crystal carries anti-reflective coating on both faces on most JLC references. Mineral glass shows a strong purple or blue glare.
- The dial prints Swiss Made at the bottom edge, below 6 o'clock.
Price benchmarks
Secondary market listings for used steel JLC Master Control references sit in the low four figures to mid five figures of US dollars, based on condition, box, and papers. A full set with the original box and certificate sells higher than a watch alone. Prices far below that range indicate a replica, a redial, or a watch with a swapped movement.
Box, papers, and service
Genuine sets include a wooden or leather box, an instruction booklet, a certificate with the serial number, and often a hang tag. Fakes copy the box with skill. The paperwork is the weak point. Print quality on the certificate is the tell. Watch for blurred type, wrong fonts, and a serial number that differs from the case back.
Brand service centers decline work on counterfeit watches. A service quote from JLC includes an authenticity check, because the watchmaker opens the case. That check is the strongest test available to a buyer.
What is not known
JLC does not publish a searchable database of every historical reference. Production totals for one reference are not public. Dial finishes changed between production years, so a small difference between two watches with the same reference does not prove a fake.
Checklist
- Ask for the reference in full, with the Q prefix.
- Request a photo of the case back and the certificate side by side.
- Compare the serial numbers.
- Have a watchmaker open the case and photograph the movement.
- Send the watch to JLC for a service estimate.