Quick answer

A fake IW371663 is a watch built by a third party and sold under IWC reference IW371663. That reference sits in the IWC Portugieser Chronograph group. Genuine watches use an IWC in-house chronograph movement and a 41 mm case. Most fakes use a stock Chinese chronograph movement, a Valjoux copy, or a quartz module. Check the movement first, then the caseback engraving, the dial print, and the paperwork.

One note: IWC ships several dial, strap, and case-metal variants inside the IW3716xx family. Confirm the dial color, strap, and case metal for IW371663 on IWC's product page before you compare a watch to it.

What the reference number tells you

IWC reference numbers start with IW. The leading digits group related models. References in the 3716 block cover the current Portugieser Chronograph line. Published specs for that line: 41 mm case diameter, steel or gold case, in-house calibre 69355, automatic winding, 28,800 vibrations per hour, about 46 hours of power reserve, two counters, and a date aperture.

Any listing that adds features IWC does not list for the reference is a warning sign.

Signs of a counterfeit

  • Movement. Look for calibre 69355. A quartz movement in a mechanical chronograph reference is a fake.
  • Subdial spacing. When a fake carries a different movement, the counters sit at the wrong distance from the center.
  • Caseback. Genuine engraving has crisp edges, and the reference and serial numbers sit in defined fields.
  • Dial print. The IWC logo and the Schaffhausen text use thin, sharp strokes. Fake print looks thick or uneven.
  • Crown and pushers. The crown screws down. The pushers have a firm stop.
  • Papers. The serial on the warranty card must match the caseback.

Checklist before you buy

  1. Open the IWC product page for IW371663. Compare case size, dial layout, and strap.
  2. Ask the seller for a photo of the caseback with the serial number.
  3. Ask for a movement photo, either through a display back or with the caseback removed.
  4. Match the serial number on the card to the caseback.
  5. Take the watch to an IWC boutique or a watchmaker who services IWC. Ask for a movement check.
  6. Compare the asking price to secondary market listings for the same reference. A large gap is a warning sign.

Market labels

Sellers use terms such as AAA, 1:1, and super clone. These labels describe marketing tiers, not factory standards. Two watches with the same label can come from different workshops with different parts. The movement and the case details are the only reliable tests.

What copies get wrong most often

The movement is the hardest part to copy. Calibre 69355 has a set bridge shape, rotor engraving, and surface finishing. Copies use stock movements with a decorated rotor. Subdial positions, date font, and crystal coating follow the movement. Buyers who check the movement first avoid most bad purchases.