Short answer

A fake IW371472 is a counterfeit of the IWC Portugieser Chronograph. The genuine watch carries a stainless steel case in the 41 mm class, a two-register chronograph dial with a 30-minute counter at 12 o'clock and running seconds at 6, a date aperture at 3, and an IWC chronograph calibre that changes with the production generation. Replicas copy the silhouette and fail on the details. Almost every fake gives itself away on one of five points: case thickness, dial printing, subdial spacing, movement finish, or caseback engraving.

What you need

  • A 10x jeweler's loupe
  • Digital calipers
  • Bright neutral light and a matte dark surface for photographs
  • Sharp reference photos of a genuine IW371472
  • A caseback tool, or a watchmaker willing to open the watch
  • A timegrapher if you want rate and amplitude numbers

1. Measure the case

  1. Let the watch sit at room temperature for ten minutes before you touch it.
  2. Measure the diameter across the bezel between 9 and 3 o'clock with calipers.
  3. Measure total thickness from the caseback to the top of the crystal.
  4. Measure the lug-to-lug distance and the lug width.
  5. Compare all four numbers with the published specification. A gap of 0.5 mm or more points to a replica case.
  6. Run a fingertip around the bezel and the lug edges. Genuine case work is chamfered and even. Cheap fakes leave a sharp lip and rough brushing.

2. Read the dial under magnification

  1. Study the IWC and SCHAFFHAUSEN printing. Genuine printing is crisp with clean edges and no ink bleed.
  2. Check the vertical alignment of the two subdials against reference photos of the reference. Replica dials often sit a fraction off center.
  3. Inspect the applied indexes for polished bevels and sharp corners. Stamped indexes look flat and dull.
  4. Look at the hands. They should be leaf shaped with a polished bevel down the center and no burrs at the tips.
  5. Examine the date aperture and the date font. Replica date wheels use wider numerals and sit deeper behind the dial.
  6. Tilt the dial toward a light source. Genuine anti-reflective coating on both faces of the sapphire produces a faint blue or purple tint with almost no reflection. Single-sided coating on a fake produces a heavy white glare.

3. Test the chronograph

  1. Press the upper pusher to start the chronograph.
  2. Let it run for 30 seconds, then press again to stop it.
  3. Press the lower pusher to reset and watch the hands return. Genuine reset snaps to zero in one motion. Replica hands often creep or land slightly off zero.
  4. Feel the pusher travel. Genuine pushers have a short, firm stroke with a clear click. A long, spongy stroke is a sign of a Valjoux 7750 clone with worn springs.

4. Open the caseback

  1. Have a watchmaker remove the caseback if you are not confident with the tool.
  2. Compare the rotor engraving with reference photos. Lettering size, spacing and depth all matter.
  3. Look at the finishing. Genuine bridges carry Geneva stripes or perlage with sharp, consistent edges. Replicas show shallow, uneven patterns and tool marks.
  4. Check the balance wheel and the regulator. An exposed regulator arm with a stud screw usually means a mass-produced clone movement.
  5. Write down the movement designation and the number of jewels, then compare both with the specification for that reference.

5. Check the caseback and serials

  1. Read the reference number and serial number under the loupe.
  2. Confirm the reference matches the dial, case and movement configuration you are looking at. Mixed parts are common on rebuilt watches sold as replicas.
  3. Check the engraving depth. Laser engraving on a fake looks shallow and grey; genuine stamping or deep engraving has crisp walls.
  4. Photograph the numbers and compare them with archive photos of the same reference.

6. Judge the strap, clasp and box

  1. Check the strap stitching and the inner lining. Even spacing and matching thread color are good signs.
  2. Inspect the clasp engraving and the folding action. Genuine clasps close with a firm, quiet snap.
  3. Treat the box and papers as supporting evidence only. They are the easiest part of a replica package to copy and the hardest part to verify.

Replica tiers and what each one gets wrong

Low-tier fakes use a cast case, a printed dial and a stock quartz or basic automatic movement. Mid-tier fakes fix the dimensions but still miss the dial printing, the crystal coating and the pusher feel. High-tier fakes copy the case and dial closely and then fall down on the movement finish, the caseback engraving and the serial format. No replica gets all five of those right at the same time. If a seller cannot show you macro photographs of the movement and the caseback before you commit, walk away.