A fake IW371615 is a counterfeit copy of the IWC Portugieser Chronograph 41, reference IW371615, a 41 mm stainless steel chronograph that runs IWC's in-house calibre 69355. The fastest way to tell it from the real watch is the back. The genuine piece has a sapphire display caseback showing a column-wheel chronograph with Geneva stripes, blued screws, and a skeletonized rotor. Most counterfeits of this reference either close the back with solid steel or hide a stock third-party chronograph behind a printed decorative plate.

Quick Authentication Checks

  1. Set the watch under a bright lamp and read the lettering at 3 o'clock with a loupe.
  2. Confirm the dial has no date window anywhere on its surface.
  3. Identify the two subdials, small seconds at 6 o'clock and a 30 minute counter at 12 o'clock.
  4. Flip the watch over and confirm the caseback is sapphire crystal, not steel.
  5. Examine the rotor through the display back for a skeletonized shape with the IWC wordmark.
  6. Look at the column wheel and levers under the balance area with 10x magnification.
  7. Read the reference number engraved on the caseback band and compare the engraving depth to the surrounding metal.
  8. Measure the case with calipers at the widest point and at the bezel.
  9. Stop the chronograph and check that the 30 minute counter jumps in single minute increments.
  10. Pull the crown out and count the positions, since a no-date chronograph has only one setting position.
  11. Compare the full specification, dial color, hands, and strap, against IWC's published data for IW371615.
  12. Ask the seller for service paperwork or an original purchase receipt before you pay.

Movement Tells

Calibre 69355 is the hardest part of the watch to copy. The genuine movement is automatic, uses a column wheel and vertical clutch, and runs at 4 Hz with roughly 46 hours of power reserve. Through the caseback you should see circular Geneva stripes on the bridges, a black or rhodium plated rotor with the IWC logo, and a freely swinging balance. Counterfeits in this reference family almost always use a Seagull ST19, an ETA 7750 derivative, or a generic Chinese automatic. Those movements show a cam-and-lever chrono layout instead of a column wheel, a different rotor shape, and rougher bevels. If the rotor is engraved rather than skeletonized, or if the bridge finish looks like ink on flat metal, the watch is not genuine.

Dial and Case Tells

  • Applied Arabic numerals sit above the dial surface with a sharp polished edge. Printed fakes look flat.
  • Feuille hands have a pronounced taper and a clean center hub. Cheap copies show thick hubs and uneven tips.
  • The minute track and railroad printing should be crisp at 10x magnification, with no bleeding into the dial.
  • Case finishing alternates polished and brushed surfaces with a hard line between them.
  • Lug width is 20 mm on the genuine case, and the lugs curve down toward the wrist.
  • The sapphire crystal has antireflective coating on both sides, which gives a faint blue or purple cast at an angle.

Caseback, Serial, and Paperwork

The reference number and serial are laser engraved on the caseback band. On a real IW371615 the engraving is shallow, even, and centered, with no burrs around the letters. Fakes often show deep stamping, uneven spacing, or a serial number that does not match the paperwork. IWC does not publish serial ranges, but an authorized dealer or IWC service center can verify a serial against their records. A watch sold without box, papers, or any service history at a price far below the used market is a counterfeit until proven otherwise.

Where Counterfeits Fail Most Often

  • Solid caseback instead of sapphire, which hides the movement entirely.
  • No column wheel under the balance, replaced by a stamped cam system.
  • Wrong subdial spacing, because a stock movement does not match the IWC dial layout.
  • Soft engraving on the caseback with a serial number that repeats across listings.
  • Pusher feel that is mushy or gritty instead of crisp and short.

Before You Buy

Buy from a seller who accepts a return window and pay with a method that offers chargeback protection. If the price is under half of the current used market value, treat the listing as counterfeit. A ten minute inspection with a loupe and calipers settles most cases before money changes hands.