The check that settles most IW371479 questions is the movement. The genuine Portugieser Chronograph carries a decorated IWC caliber under a signed rotor, and a counterfeit has to imitate that decoration on top of a stock chronograph base. Work through the movement first, then the dial, the case and caseback, the strap hardware, and finally the paperwork. Each step below lists what the test is good for, where it stops being decisive, and the situation where it earns its place in your check order.

1. Movement and rotor decoration

Older references in the 3714 Portugieser Chronograph line use the 79350, a reworked Valjoux 7750 base, while later versions move to the in-house 69355. Both show grained bridges, blued or polished screws, and crisp engraving of the caliber number and IWC branding. Fakes show the correct layout with soft, stamped lettering and a rotor whose finish is a decal rather than a machined surface.

  • Pros: Hardest feature to copy at low cost, so it separates serious replicas from cheap ones.
  • Pros: Engraving depth and font weight stay readable under a loupe where printing on dials does not.
  • Cons: Needs a caseback removal or a clear macro photo, which most casual sellers will not provide.
  • Cons: A well-built counterfeit can use the same base caliber, so layout alone proves nothing.

Use it when: the seller offers movement photos or allows an inspection by a watchmaker before payment.

2. Dial, hands, and subdial layout

On the 3714 family the chronograph minutes sit at 12 and the running seconds at 6, with the date aperture at 3. Genuine printing is thin, level, and spaced with air around it. Applied indices have polished facets that catch light along one edge. Fakes show thicker text, indices that sit flat, and subdial rings that crowd the center of the dial.

  • Pros: Visible in ordinary photos, so you can screen a listing before contacting anyone.
  • Pros: Hand shape and facet angles are expensive to reproduce at scale.
  • Cons: Dial refinishing on genuine watches muddies the comparison.
  • Cons: Photo compression hides the exact traits you are looking for.

Use it when: you are filtering a long list of listings and need a fast reason to drop the weakest ones.

3. Case, crystal, and caseback engraving

Case diameter, lug profile, and crown shape change between references, so confirm the numbers for IW371479 itself before judging dimensions. The reference number, serial, and case material are engraved on the caseback. On genuine pieces the engraved lines are sharp and the metal around them is clean. On fakes the lettering looks etched or lasered, with soft edges and inconsistent depth.

  • Pros: Serial and reference give you something concrete to verify against IWC records.
  • Pros: Caseback photos are standard in most listings.
  • Cons: Engraving can be polished away or re-cut during service.
  • Cons: A swapped caseback on a genuine case defeats the check.

Use it when: you have a serial number and want to confirm it against the reference the seller claims.

4. Strap, buckle, and clasp hardware

Genuine straps carry even stitching, tapered edges, and a signed buckle or deployant with engraving that matches the caseback in style and depth. Replacement straps are common on genuine watches, so treat this as supporting evidence rather than a verdict.

  • Pros: Quick to judge from a single clear photo.
  • Pros: Cheap fakes often reveal themselves here first.
  • Cons: Aftermarket straps on real watches are normal.
  • Cons: Hardware is the easiest part to swap out.

Use it when: you need one more signal to confirm what the movement already suggested.

5. Box, papers, and service history

Boxes, warranty cards, and manuals are reproduced in quantity, so they support a case rather than make one. What matters is whether the serial on the card matches the caseback and whether service records name a real watchmaker or service center.

  • Pros: Matching serials across documents point to a single original watch.
  • Pros: Service records explain polishing, parts swaps, and dial changes.
  • Cons: Full sets exist for fakes and are sold separately online.
  • Cons: Missing papers are common on older references and prove nothing.

Use it when: two watches are otherwise equal and you need a tiebreak.

Which check to run first

  1. Buying from a photo listing: start with the dial and caseback, then ask for movement photos before moving forward.
  2. Buying in person: start with the movement, then verify the serial against the reference.
  3. Evaluating your own watch: start with the movement, since dial and strap may have been changed over the years.
  4. Comparing two candidates: rank them on movement, then caseback engraving, then paperwork.

No single trait decides the question on its own. Movement, dial, case, hardware, and documents together build the case, and the movement carries the most weight of the five.