Short answer
3748410 is a Jaeger-LeCoultre reference number, not a serial number. A watch sold as "3748410" in the replica market is a counterfeit built to look like a Reverso Classic. Real ones cost four figures used and five figures new. Fakes sell for 200 to 600 US dollars. Three checks settle most cases: the sliding carriage on the Duoface, the depth of the caseback engraving, and the finish on the manual-wind movement.
What the number tells you
Jaeger-LeCoultre reference numbers do not decode from a public formula. The 374 block is used across Reverso Classic models, and one reference can cover a case size, a dial layout, and a calibre. Confirm the exact model, case size, and movement against the Jaeger-LeCoultre catalogue or a written extract from the manufacture archive before you rely on the number alone. A seller who cannot name the calibre behind 3748410 has not handled a real one.
Reference and serial are different fields. The reference sits on the caseback and the paperwork. The serial sits on the caseback and the movement bridge, and the two must match. Replica batches often print one serial across many units.
Why this reference gets copied
The Reverso is a simple shape on the outside and a hard shape to fake on the inside. The case is a rectangle with straight lines, so a machined copy looks close in photos. The Duoface adds a second dial and a sliding carriage, which is where copies break down. Counterfeiters ship the easy parts and skip the mechanism.
Checks on the watch
Case and caseback
The Reverso case flips on tracks inside the outer frame. Real carriages move with even resistance and no side play. Copies rattle, bind at the ends, and show tool marks inside the tracks. Caseback engraving on a real JLC is cut with consistent depth and sharp edges. Copies show shallow etching, wrong letter spacing, and a soft "Reverso" script.
Second dial and carriage
A Duoface carries two dials on one movement. The second dial sits on the back of the carriage and is set by a slide or a crown position, not a pusher. A watch with a pusher in the caseband that claims Duoface function is wrong. Measure the case thickness with calipers. Two dials add height, and copies that reuse a single-face case come in thin.
Movement
The Duoface line uses manual-wind calibres in the 854 family: about 21,600 vibrations per hour and roughly 42 hours of reserve. Real finish shows Geneva stripes with clean borders, blued screws, and perlage under the balance. Copies show stamped plates, painted stripes, and screws with soft slots. A watchmaker with a case knife answers this in five minutes.
Dial, hands, and printing
Real dial text is pad printed with sharp edges and matched font weight across both dials. Copies show dot gain, thicker strokes, and mismatched fonts between front and back. Real hands are faceted and polished. Copy hands are stamped, and the edges round off under a loupe.
Strap, buckle, and hardware
Real buckles carry a signature with crisp edges and correct hallmarks on gold pieces. Copy buckles show soft edges and a shallow stamp. Strap stitching on a real JLC is even at the keeper and the tip.
Box, papers, and price
Ask for the warranty card, the booklet, and the service history. A price far under market is the strongest signal. Used Reverso Classic Duoface examples trade in the four figures. New retail sits near five figures in USD. Nothing in the 300 dollar range is a Jaeger-LeCoultre.
US legal exposure
Counterfeit watches are seizable at import under 19 U.S.C. § 1526, and trafficking in them is a federal offense under 18 U.S.C. § 2320. Selling a copy as an original adds fraud exposure under state law. Buying for personal use is a different question from reselling, and seizures happen either way.
Before money changes hands
- Get the reference and serial in writing, with photos of both.
- Request a movement photo with the caseback off.
- Confirm calibre, case size, and dial layout against JLC.
- Buy from a seller with a written return window.
- Have an independent watchmaker open the watch on arrival.
If a seller refuses any of these steps, treat the watch as a copy and walk.