Short answer

A fake IW371429 is a counterfeit of the IWC Portugieser Chronograph. The fastest test is the movement. The genuine watch uses an IWC calibre 69355 in current production, or a 79350 in older pieces. Many fakes use a Chinese copy of the Valjoux 7750. Read the rotor, the bridges and the finish through the display back. The second test is case thickness. The real watch measures about 12.3 mm to 13.1 mm depending on generation. Replicas run 14 mm to 15 mm because the 7750 stack is taller.

What the reference is

IW371429 belongs to the IWC Portugieser Chronograph line. The family uses a steel case of about 41 mm, a bi-compax dial with chronograph minutes at 12 and running seconds at 6, a date at 3, sapphire crystal front and back, and 30 m water resistance. Lug width is 20 mm. Calibre 69355 has a 46 hour power reserve at 28,800 vph. The older 79350 runs 44 hours. Production spans several generations, so confirm dial color, strap and movement against the IWC reference listing before you judge one watch.

Checks in order

Case and crystal

  • Measure thickness with calipers. Over 14 mm is a warning sign.
  • Inspect lug shape and the polish on the bevels. Fakes show soft edges and rounded corners.
  • Sapphire sits flat and clear. Mineral glass on a fake scratches with a steel pin.

Dial

  • Applied numerals and leaf hands are faceted, not stamped flat.
  • Subdials carry fine concentric snailing. Printed rings look flat under a loupe.
  • Text spacing: the IWC logo and SCHAFFHAUSEN line match reference photos.
  • Date cutout edges are crisp. Fakes show burrs and off-center numbers.

Movement and caseback

  • The sapphire back shows a decorated rotor and blued screws. A blank or rough movement is a fake.
  • Reference and serial numbers are engraved on the caseback rim. Compare font weight and depth.
  • Chronograph pushers have a short, firm travel. 7750 clones feel spongy, and the chrono seconds hand stutters at start.

Papers and price

No genuine IW371429 sells far below market. A price 60 percent under the going rate is a red flag. Ask for the warranty card, the box and a service receipt. An IWC service center can verify a serial number and authenticate a watch in hand.

Legal note

Counterfeit watches are illegal to import and sell in the United States. US Customs can seize a shipment. A fake carries no warranty and no service support from IWC.