Short Answer
Most fake IW371790 watches fail in three places: the caseback engraving, the dial and hands, and the movement. Real IWC engraving is cut with sharp, uniform letterforms and a depth you can feel with a fingernail. Counterfeit engraving looks shallow, hazy, or laser-burned under 10x magnification. If you find three or more mismatches on the checklist below, treat the watch as a fake and walk away.
What You Need Before You Start
- A 10x loupe or a phone macro lens
- Digital calipers and a kitchen scale accurate to 1 gram
- Catalog photos of the exact variant, including dial color, case metal, and strap
- Seller photos of the dial, caseback, crown side, movement, and clasp
- A jeweler or watchmaker who can open the caseback
Step-by-Step Authentication Checks
- Photograph the caseback in flat light and write down the reference number and serial number.
- Confirm the reference prints as IW371790 with correct spacing and font size, then compare it to the published spec for your exact variant.
- Inspect the engraving depth with a loupe, checking that letterforms have crisp edges instead of a soft, etched haze.
- Compare the dial text to reference photos, looking at the brand logo, the model line, and the subdial labels for edge sharpness and even spacing.
- Check subdial alignment and hand reset, since both hands should return to zero with no drift.
- Examine the date window, checking that the frame is clean and the date font matches the reference image.
- Study the hands and applied indices under magnification for polished bevels, even lume fill, and no glue residue.
- Look at the crystal for a faint blue or violet anti-reflective tint, a feature copy watches often skip.
- Work the crown and pushers, checking that winding feels smooth and pusher travel is short and crisp.
- Weigh the watch head and measure the case diameter, then compare both readings with the spec for your reference.
- Have a watchmaker open the caseback and photograph the movement, including the rotor, bridges, and jewel count.
- Cross-check the box, warranty card, and manual, confirming the card serial matches the caseback serial.
Common Tells on IW371790 Fakes
- Serial number on the caseback does not match the number engraved on the movement.
- Caseback text sits on a rough surface with visible tool marks.
- Chronograph seconds hand does not snap back to 12 when reset.
- Subdial hands sit off-center or shift after a few seconds of running.
- Crown feels loose, or the pushers need long travel to engage the chronograph.
- Dial text has soft edges, uneven letter spacing, or a typeface that differs from the original.
- Lume plots are uneven, with glue visible around the markers.
- Strap or bracelet hardware has sharp clasp corners and brushing that does not match the case.
Paperwork and Serial Verification
Fake sets often arrive with a box that looks close and papers that do not. Check that the warranty card serial, the caseback serial, and the movement serial all agree. Send the serial to IWC service and ask for a records check. A watch that has no service history and no matching serials is a fake in most cases.
If You Already Bought a Fake
Stop wearing the watch, keep the listing and payment records, and open a dispute with your payment provider. Report the seller to the marketplace and to your local consumer protection office. Do not resell it as a genuine IWC, since that turns a bad purchase into a legal problem.