Short Answer
3518420 is a seller catalog code, not a Jaeger-LeCoultre reference number. Genuine JLC references start with the letter Q and carry seven digits, such as Q1548420 or Q1368420. When a replica page shows 3518420, it points to the dealer's own listing, and the Q number behind it tells you which real model the replica copies. Find the Q number first, then judge the replica against the original.
Why 3518420 Does Not Appear in Any JLC Catalog
Jaeger-LeCoultre labels every model with a Q prefix followed by a seven digit string. Dealers who stock replicas often drop the Q and shave a digit to create a short SKU they can search and track. That is why 3518420 returns nothing on the brand site and why a search for it leads to vendor pages instead.
The code usually sits close to references from the Master Control and Master Ultra Thin families. Both use round cases, thin bezels, and applied baton markers, which are the details a replica has to match.
What You Need Before You Compare
- A photo of the genuine model with the full Q reference
- Case diameter and thickness figures for that reference
- A jeweler's loupe or a phone macro lens
- Daylight, not a warm indoor bulb
How to Inspect a Replica JLC Step by Step
- Measure the case with calipers and compare the result to the published diameter. A 39 mm Master Control Date that measures 40.5 mm is a different case, not a tighter tolerance.
- Check the thickness. Genuine JLC automatics sit near 9 mm. Replicas built on a generic rotor stack often reach 11 mm or more.
- Turn the watch over and read the caseback engraving. Genuine text is laser etched with crisp edges. Stamped or pad printed text looks soft and shallow.
- Look at the crown. The JL logo should be sharp and centered on the flat face, not off to one side or blurred.
- Study the dial printing under magnification. The brand name, the Swiss Made mark at six o'clock, and the minute track should all hold clean edges.
- Check the applied markers. Each one should sit flat, reflect light evenly, and line up with the printed track beneath it.
- Angle the watch toward a window and look at the crystal. A sapphire crystal with anti-reflective coating almost disappears. Mineral glass throws a grey or purple haze.
- Watch the seconds hand sweep. A smooth sweep suggests a 28,800 vph movement. A visible stutter points to a lower beat rate.
- Wind and set the watch. The crown should move through the positions with defined clicks. Gritty or loose action is a common replica fault.
- Time the watch over 24 hours with a phone app. Anything beyond plus or minus 15 seconds a day needs regulation or a better movement.
Movement: The Part Photos Hide
Replica pages rarely show the movement. Two families dominate this market: Chinese automatic calibres from Seagull and Hangzhou, and Japanese Miyota units. Both can keep time, and both differ from the in-house JLC calibres they imitate. Genuine finishing uses Geneva stripes, blued screws, and engraved bridges. Replica plates are often printed or stamped to look decorated, and the engraving flattens under a loupe.
Common Red Flags
- A price far below the rest of the replica market for the same model
- No movement photo, no caseback photo, and no measurement list
- Stock images taken from the brand site instead of photos of the actual unit
- A reference number that returns zero results anywhere except the seller's own pages
What a Solid Replica of This Model Should Do
A good replica of a Master Control style watch copies the proportions first: 39 mm wide, about 9 mm thick, 20 mm lugs. It should use sapphire crystal on both sides, an applied logo, and a movement that hacks and hand winds. Ask the seller for a photo of the actual watch on a scale and beside a ruler. If they refuse, buy somewhere else.