Quick Answer

A fake IW371469 gives itself away at the case, the dial furniture, and the caseback. The genuine watch is part of the IWC Portugieser Chronograph IW3714 family: a 40.9 mm stainless steel case, a two-register chronograph with small seconds at 6 o'clock and a 30-minute counter at 12 o'clock, applied polished numerals, feuille hands, and IWC calibre 79350, a heavily reworked Valjoux 7750 with a 44-hour power reserve. Most counterfeits fail on at least two of those points. Measure the case first, then inspect the dial, then look at the movement through the display back.

Prerequisites

  • Digital caliper with 0.01 mm resolution
  • 10x jeweler's loupe
  • Bright, diffused light or a daylight lamp
  • Timegrapher (optional, but useful for the movement check)
  • Clear reference photos of a genuine IW371469 from the IWC archive or a dealer listing
  • A watchmaker you trust for a final opinion

Step-by-Step Authentication

  1. Measure the case diameter across the bezel at 3 and 9 o'clock. The genuine reference measures 40.9 mm, so a reading of 42 mm or more points to a counterfeit case.
  2. Measure the lug width at 12 o'clock. Genuine lugs take a 20 mm strap, while many fakes are cut for 21 or 22 mm.
  3. Tilt the crystal toward the light at roughly 45 degrees. Genuine sapphire has anti-reflective coating on both faces, so the glass almost vanishes with a faint blue tint, while fakes look milky or green.
  4. Study the numerals and hands under the loupe. Genuine markers are applied, polished, and stand off the dial with sharp edges, and the leaf hands taper to a fine point.
  5. Read the dial text. The IWC block letters, the Schaffhausen line, and any Chronograph or Automatic wording should be thin, evenly spaced, and free of ink bleed.
  6. Check the subdial layout. Small seconds sit at 6 o'clock and the chronograph minutes counter sits at 12 o'clock, with no date window at 3 o'clock on this reference.
  7. Press the chronograph pushers. A genuine watch starts, stops, and resets with a crisp click and the hands snap back to zero, while fakes feel spongy and drift on reset.
  8. Read the caseback engraving. The reference number IW371469, a serial number, and the Probus Scafusia phrase should be laser-engraved with crisp, shallow lines, not deep stamped.
  9. Look at the rotor through the sapphire back. Calibre 79350 shows Geneva stripes, blued screws, and IWC markings on the rotor and the bridge.
  10. Run the watch on a timegrapher for a minute. A healthy calibre 79350 holds an amplitude near 280 to 310 degrees with a beat error below 0.5 ms.

Common Fake Giveaways

  • The rotor carries fake engraving over a stock 7750, or the movement is a Chinese 7750 copy with no decoration.
  • The minute track is printed too thick, and the subdial rings are misaligned with the hands.
  • The crown is unsigned or the pushers sit at uneven heights.
  • The caseback font does not match the IWC house typeface, and the serial repeats across different listings.
  • The strap is stamped with a logo the reference never used, or the buckle is a generic tang.

When to Bring In a Watchmaker

If the case measures correctly but the dial or movement still feels off, hand the watch to a watchmaker with IWC experience. A bench check of the movement, the balance, and the case finishing settles the question in minutes, and a written opinion protects you if you are buying from a private seller. Ask for movement photos before you pay, and compare them side by side with photos of calibre 79350.