Short answer

The IW371625 is a reference from IWC's Portugieser Chronograph family, and it does get copied. It is also one of the harder watches to fake convincingly. The genuine watch uses an in-house chronograph calibre, a 41 mm case built to tight tolerances, and a dial packed with details most replica factories leave wrong. With the watch in hand, a loupe, and a photo of a known-genuine example, you can usually reach a verdict in ten minutes.

Here is the order I work in, from the cheapest check to the ones that need tools.

First, confirm what IW371625 should actually be

Look up the reference before anything else. Case material, dial colour, strap type, and whether it was a limited or boutique release all matter, because replica sellers mix and match. A common move is to take a case they already produce, drop in a different dial, and print a reference number that looks plausible. If the dial colour in front of you was never offered on IW371625, stop there.

Case size, thickness, and weight

The steel Portugieser Chronograph in the 3716xx line measures 41 mm across and about 13.1 mm thick, with 3 bar of water resistance. Thickness is where fakes slip. A counterfeit built on a Valjoux 7750 base usually lands a millimetre or more thicker, and you can feel that when the watch sits on the wrist or slides under a shirt cuff. Put it on a caliper if you can. On leather, a genuine steel example comes in somewhere around 80 to 95 grams depending on the strap.

Check the lug gaps as well. Real lugs sit tight against the strap with even spacing and no light showing through. Fakes often have a wider gap and a strap that was cut to fit rather than made for the case.

Movement and caseback

The 3716xx Portugieser Chronograph runs IWC's in-house 69355: automatic, 4 Hz, roughly 46 hours of power reserve, visible through a sapphire caseback. The finishing is the tell. You should see Geneva stripes on the bridges, clean bevelled edges, and a signed oscillating weight. Replicas either use a decorated 7750 or a Chinese chronograph movement with a rotor carrying an IWC logo stamped in the wrong font, and the bridges never match the shape of the real thing.

Compare the rotor and bridge layout side by side with a photo of a genuine 69355 before you spend money. That one comparison kills most fakes.

Dial printing and applied numerals

  • Applied numerals should be polished on the bevels, so the edges catch light and the faces shift as you tilt the watch. Stamped fake numerals look flat and dull.
  • The printed railway minute track should be razor sharp under magnification. Fake printing looks slightly fuzzy or heavy.
  • Lettering and logo weight should match the reference exactly. Font substitutions show up fast with a loupe.
  • Subdial hands should reach their markers cleanly, with a counterweight shaped like the original. Fakes often run short or cut the counterweight wrong.

Pushers, crown, and crystal

Press the chronograph pushers. On a genuine IWC chronograph they feel crisp, with short, even travel and a clean reset. Cheap fakes feel spongy or gritty, and the reset sometimes hesitates. The crown should be signed and should turn with light, even resistance.

The crystal is a quick check. Genuine Portugieser Chronographs use sapphire with anti-reflective coating on both sides, so the dial looks like it is sitting in open air with almost no reflection. Most fakes are uncoated or coated on one side, and they flash a heavy blue or purple tint under a light.

Paperwork, price, and the law

Ask for the guarantee card, the original invoice, and any service history. Send the serial to IWC or take the watch to an authorised service centre for authentication. Then look at price. If someone asks a small fraction of the going rate for IW371625, the watch is not a bargain, it is a counterfeit. Counterfeit watches are illegal to import into the United States and can be seized and destroyed, and selling them carries real legal risk.

Bottom line

Most fake IW371625s fall apart on three checks: the movement layout under the caseback, the case thickness, and the dial printing. Get photos of a known-genuine watch, work through the list above, and pay for professional authentication before money changes hands. That is cheaper than a mistake.