The short answer
A fake carrying the IW938437 reference and a genuine IWC differ in four checkable places: the caseback engraving, the dial printing, the crown and pusher feel, and the finishing on the movement. Replica makers copy the outline of the case well because that is what photographs sell. They copy the small text, the engraving depth, and the hidden finishing poorly, because those cost machine time and hand work.
If a listing shows an IW938437 at a price far below market, assume it is a copy until the four checks below pass. Most sellers of counterfeits avoid close, angled photos of the caseback for exactly this reason.
Before you start
- A 10x loupe, or a phone with a macro mode
- A bright light you can angle across the metal surface
- The seller's photos at full resolution, downloaded, not screenshots
- The reference number and serial number as they appear on the caseback
How to compare, step by step
- Ask the seller for a straight-on photo of the caseback and a second photo taken with light raking across it from the side.
- Read the reference and serial number. On a genuine IWC the characters are cut deep into the metal, sit on a single baseline, and use the brand's own typeface.
- Run your loupe along the edge of each engraved character. Genuine engraving has a crisp wall. Laser-etched fakes look shallow, slightly rounded, and grey rather than bright.
- Compare the dial text next. Look at the weight of the brand name, the spacing between letters, and whether the printing sits level with the applied indices.
- Check the indices and hands under the loupe. Genuine applied markers have polished bevels and sit flush. Copies often show glue residue, uneven polishing, or a marker set a fraction off center.
- Operate the crown. Screw it down and unscrew it. Genuine threads engage in a short, clean turn with no wobble and no grinding.
- Press any pushers. They should travel with resistance and snap back on their own. Mushy or rattling pushers point to a cheap module inside.
- Look through the display back if the watch has one. Compare rotor engraving, screw heads, and the finish on the bridges against reference photos of the same caliber.
- Weigh the watch and measure the case with calipers. Published dimensions and weights for the reference make a fast filter, and copies usually run light.
- Inspect the clasp or buckle engraving and the strap stitching. This is the part most copies rush, and it shows.
- Write down the reference and serial number and send them to IWC service or an authorized watchmaker for a records check.
- Ask for the service history, the original papers, and the box, then match every printed number against the watch itself.
Red flags that end the comparison
- The reference number is spelled with the wrong letter or digit pattern, or the font changes inside the same line.
- Dial text sits crooked relative to the indices, or the print looks thicker than reference photos.
- The caseback is blank, laser-marked, or covered by a sticker hiding the number.
- The seller refuses a movement photo or a caseback photo in daylight.
- The price is far under the market range for the reference, and the seller calls it a factory second or an employee sale.
Why the numbers rarely match
Reference and serial numbers on genuine watches are recorded by the manufacturer, and a service center can confirm whether a given pair belongs to a real case. Counterfeiters reuse a small pool of numbers across thousands of units, so the same serial appears on listings in different countries. If two sellers show the same serial on the same reference, at least one is selling a copy.
If you already own a copy
Treat it as what it is: a replica built to look correct at arm's length. Do not send it to a brand service center, since they will not work on it and may keep it for inspection. A local independent watchmaker can service the movement, reseal the case, and replace gaskets so the watch stays wearable.