How to Spot a Fake IW371748

A counterfeit IW371748 gives itself away at the crystal, the subdials, and the caseback. Genuine Portugieser Chronographs in the IW3717 family use a 41 mm steel case, a domed sapphire crystal with antireflective coating on both faces, and the in-house caliber 69355 with a column-wheel chronograph. Copies match the silhouette and miss the finishing, the proportions, and the movement layout. Work through the checks below before you accept any IW3717 as genuine.

Before You Start

  • A 10x jeweler's loupe
  • Calipers or a ruler marked in millimeters
  • A bright, diffused light source
  • The seller's paperwork listing reference and serial number

Step-by-Step Checks

  1. Measure the case across the bezel, not including the crown. A genuine IW3717 sits at 41 mm wide and about 13 mm thick. Copies come in at 40 mm or less, or run thick because the case has to hold a heavier third-party movement.
  2. Tilt the watch under a light. The real crystal domes upward and coats both faces, so the dial stays readable from sharp angles with almost no haze and no mirrored glare. A flat crystal or a single-coated one with a strong color cast is a warning sign.
  3. Study the two subdials. Small seconds sit at 6 o'clock, elapsed chronograph minutes at 12. On a genuine dial the recessed rings are cut deep with fine circular graining, and the hands clear the printed track. Copies show stamped or shallow rings, coarse graining, and hands that sit too high.
  4. Check the hands. Genuine leaf-shaped hands are polished on the flanks with clean edges, and the tips reach the printed minute track. Copies carry flat painted hands or hands that stop short of the track.
  5. Read the caseback engraving through the loupe. Genuine text is cut into the steel with crisp walls, and the reference and serial numbers sit between the lugs. Laser etching looks shallow, soft, or raised at the edges. A caseback rating above the 3 bar IWC specifies is another flag.
  6. Inspect the movement through the display back. Caliber 69355 shows a column wheel, Cotes de Geneve stripes, perlage, blued screws, and a signed rotor. Earlier IW3714 references use the 79350, a Valjoux 7750 base with a rotor that wobbles when you shake the watch. Copies carry undecorated ETA or Seagull clones with no column wheel.
  7. Compare the weight and the strap hardware against a known genuine example. The buckle is signed and the stitching is even. Copies feel light in the hand, use stamped hardware, and show a plastic sheen on the strap.
  8. Confirm the reference and serial number with an IWC boutique or authorized service center. Staff can verify the number and open the case to confirm the caliber.

Limits of a Visual Check

Polished cases, swapped dials, and rebuilt movements defeat any inspection done by eye alone. A watch can carry a genuine case and a copy movement, or the reverse. Buy only from sellers who supply the original invoice and warranty card, and treat any refusal to allow a service-center inspection as a refusal to sell.

Counterfeit watches are illegal to sell in most jurisdictions, carry no manufacturer warranty, and cannot be serviced by IWC. A genuine IW3717 holds value and can be repaired for decades. A copy cannot.