Quick answer

A fake IW371785 fails on three checks: the chronograph movement, the dial printing, and the caseback engraving. Ask the seller for a photo of the movement with the caseback removed, a macro shot of the dial at 12 o'clock, and the serial number. If the seller refuses any of the three, walk away.

What the reference number covers

IW371785 sits in the IWC Portugieser Chronograph family. Public spec sheets for this exact number are hard to find, so confirm the reference with IWC or an authorized dealer before you pay. The line shares these traits:

  • Case diameter 41 mm on current production, about 40.9 mm on older 3714 references.
  • Two subdials: chronograph minutes at 12 o'clock, running seconds at 6 o'clock.
  • Sapphire crystal with anti-reflective coating on both sides.
  • Water resistance 3 bar (30 m).
  • Alligator leather strap, 20 mm lug width.
  • "Swiss Made" printed under the 6 o'clock subdial.

1. Movement

Current Portugieser Chronograph watches run IWC calibre 69355, an in-house automatic with a column wheel. It beats at 28,800 vibrations per hour. Power reserve is about 46 hours. Older 3714 references used calibre 79350, a modified Valjoux 7750 with a 44-hour reserve.

Replicas use Seagull ST19 hand-wound movements or Chinese clones of the 7750. Signs of a fake:

  • Rotor wobble and noise when the watch is turned. A 79350 rotor winds in one direction and free-spins in the other.
  • Pushers that grind or stick. Genuine chronograph pushers move with light, even pressure.
  • Chronograph seconds hand that stutters instead of sweeping.
  • Subdial hands that jump in one-second steps. The running seconds on a 69355 sweeps.

2. Dial and hands

Genuine dials carry applied numerals and leaf-shaped hands with polished bevels. Printing is crisp under 10x magnification. Check these spots:

  • Letter spacing in "IWC" and "Schaffhausen". Replicas crowd the letters or use a heavier weight.
  • Date window edges and alignment. A crooked date aperture points to a fake.
  • Subdial rings. Genuine rings are thin and even. Fake rings look thick or painted.
  • Hands. Fake leaf hands have flat sides and no bevel.

3. Case and caseback

Genuine cases mix polished and brushed surfaces with sharp transitions. Caseback engraving is deep and consistent: reference number, serial number, model name, hallmarks. Fakes show shallow laser etching, uneven fonts, and missing digits.

IWC serial numbers run 8 digits and sit on the caseback and, on many references, on the movement bridge. The two numbers should match the paperwork.

4. Price and paperwork

New Portugieser Chronograph watches retail around 8,000 to 9,000 US dollars. Pre-owned examples trade around 5,500 to 7,000 US dollars. Replica listings ask 300 to 900 US dollars. A "new" IW371785 at 1,200 dollars is not genuine. Box, warranty card, and service receipts add proof but can be faked. Treat them as supporting evidence, not proof.

5. Limits of online checks

Photos hide movement quality, weight, and finish. Dial macros catch printing errors. Caseback shots catch engraving errors. Neither shows how the chronograph feels in the hand. For any purchase above 2,000 US dollars, meet a watchmaker or an authorized service center and pay for an inspection.