Short answer
3988420 is not a Jaeger-LeCoultre reference number. Modern Jaeger-LeCoultre references start with the letter Q and carry seven digits, for example Q3858522 or Q2548520. A bare seven-digit string like 3988420 comes from a marketplace listing or a replica seller's internal product code. That alone does not prove a watch is counterfeit. It does mean the number cannot be checked against a factory catalog.
What the Reverso is
Jaeger-LeCoultre launched the Reverso in 1931 for polo players. The case sits on two machined rails and flips over to protect the crystal. The rails are the part replica makers get wrong most often because they require tight tolerances on both the carriage and the case frame.
Case checks
- Slide the carriage. On a genuine Reverso the movement is smooth and stops at the end of the track. Fakes bind, wobble, or rattle.
- Look at the engraving on the back of the case. Genuine engraving is cut into the metal and shows depth under a loupe. Laser etching on fakes looks flat and gray.
- Measure the case with calipers. Replica listings quote dimensions that often do not match the shipped watch.
- Check the crown. It should sit flush, turn with firm clicks, and line up with the case band.
Dial and hands
Authentic Reverso dials use applied indexes on most references. The printing is crisp at 10x magnification. Replica dials show thick ink, uneven gaps between numerals, and hands with rough edges. Lume on a Reverso Classic is minimal. Heavy glowing markers on a Classic reference are a warning sign.
Movement
Reverso Classic and Duoface models use in-house manual movements, such as calibre 822, running at 21,600 vibrations per hour with about 42 hours of power reserve. A seconds hand that jumps once per second means a quartz movement, not a mechanical one. A rotor that spins when you shake the case means an automatic movement, which does not belong in a Reverso Classic.
Numbers and papers
Genuine pieces carry a case number and a reference, and both are recorded in the Jaeger-LeCoultre archive. A boutique or an authorized service center can pull that record and confirm the build. Replica sellers give numbers that do not match any record, or no number at all. Ask for clear photos of the caseback, the movement, and the warranty card before you send money. A seller who refuses those photos is a risk.
US legal note
Trafficking in counterfeit goods is a federal crime in the United States under 18 U.S.C. 2320. US Customs and Border Protection seizes counterfeit shipments at the border. Buyers who wire money to overseas replica sellers have no chargeback path in most cases, and the loss is not recoverable.
Checklist
- Confirm the reference starts with Q and has seven digits.
- Ask for caseback and movement photos.
- Slide the carriage and test the flip.
- Check the beat rate: 21,600 vph for calibre 822.
- Verify the case number with a service center.