Fake IW371752: The Short Answer
Reference IW371752 sits inside the IWC Portugieser Chronograph family, a line copied in China more than almost any other dress chronograph. Genuine 3717-series watches were built with a case of about 40.9 mm, a dial with chronograph counters at 12 and 6 plus running seconds at 9, and IWC caliber 79320, a reworked Valjoux 7750. A counterfeit fails on at least one of those three points, and most fail on two.
If you searched this reference, you likely hold a secondhand watch or a marketplace listing and need a verdict. The procedure below takes roughly half an hour with basic tools. It removes the common fakes from the table. It does not replace a watchmaker opening the case.
Prerequisites
- A 10x jeweler's loupe
- Digital calipers
- Bright, diffuse light, such as a window in daytime
- A genuine photo set for the exact dial variant you are checking
- A watchmaker willing to open the caseback
How to Check a Suspected Fake IW371752
- Confirm the factory spec for your exact variant first. IWC used several dial colors and case metals under the 3717 block, and the numbers differ between them.
- Measure the case across the bezel at 3 and 9 o'clock with the crown excluded. Genuine cases read 40.8 to 41.0 mm. Copies often run 42 mm or wider because the builder stuffed a stock case around an off-the-shelf movement.
- Measure case thickness and lug width against the reference chart. A case that is 1 mm or more thick is a strong sign of a stock Chinese case.
- Check subdial placement. The chronograph counters must sit at 12 and 6, the small seconds at 9. Counters pushed toward the center mean a movement with a different geometry.
- Inspect the dial print under the loupe. The brand name, the "Automatic" line, and the chronograph scale should have crisp, unbroken serifs with no ink bleed or fuzzy edges.
- Examine the hands. They are leaf-shaped, polished, and set at the correct length, with the chronograph hand reaching the outer track.
- Turn the crown and press the pushers. Winding is smooth, the date flips cleanly at midnight, and the chronograph starts, stops, and resets with a firm click.
- Ask the watchmaker to open the caseback. Genuine watches carry caliber 79320 with IWC markings, striped or circular graining, and a signed rotor. Quartz movements, unmarked 7750 clones, and Dubois-Depraz modules are immediate disqualifiers.
- Read the caseback engraving. Reference number, serial, and the brand name should be cut deep and even, not laser-printed on a flat surface.
- Weigh the watch in your hand. A steel Portugieser Chronograph has heft. Light, hollow-feeling cases point to plated brass or thin stainless.
- Check the strap or bracelet hardware. Buckle and clasp signatures are engraved, not stamped, and the leather shows grain rather than a uniform plastic surface.
- Cross-check the serial number against the reference number on the caseback and in the paperwork. Mismatched pairs are the single most common tell on the secondhand market.
- Get a written opinion from a watchmaker before you pay. That one step settles everything above.
Dial and Case Tells That Decide Most Cases
- Subdial rings that are printed rather than recessed
- A date window with sharp, unpainted edges versus a rough cut
- Pushers that sit flush and unscrew on the genuine watch instead of protruding
- Lugs that taper the wrong way or show tooling marks at the spring bar holes
- An anti-reflective coating that shows a blue or green cast
What Fakes Get Right
Copy makers have solved the dial from three feet away. Photos on a listing page rarely expose a counterfeit. The tells live in the measurements, the movement, and the engraving, which is why an in-hand check beats an image review every time.
If the Watch Fails
Stop the payment if you can, document the serial and reference number with photos, and report the listing to the platform. If you already paid, a written authentication report from a qualified watchmaker is the document that supports a refund claim or a chargeback.