Short answer
No published IWC reference number reads "IW371717." The base reference is IW3717, the Pilot's Watch Chronograph sold from about 2006 to 2012. The trailing "17" is a seller tag, not an IWC code. A watch listed as a fake IW371717 is a counterfeit copy of ref IW3717: a 42 mm steel chronograph with three subdials, a day-date window at 3 o'clock, and a black or silver dial.
What the real IW3717 is
- Case: stainless steel, 42 mm across, 14.7 mm thick, 60 m water resistance.
- Movement: IWC calibre 79320, based on the Valjoux 7750, 28,800 vph, about 44 hours of power reserve.
- Dial: counters at 6, 9 and 12 o'clock, day-date at 3 o'clock, soft-iron inner case for magnetic shielding.
- Crystal: sapphire with anti-reflective coating on both faces.
- Production years: 2006 to 2012. The ref 3777 replaced it.
IWC adds two digits to the base number to mark dial and strap variants, such as IW371701, IW371704, IW371705 and IW371710. "17" is not one of those suffixes. A listing that calls a watch an IW371717 is using an invented code, and the code tells you nothing about the case, dial or movement inside.
Signs a copy is a copy
- Subdial layout. The real watch uses the 7750 layout at 6, 9 and 12. Copies built on another base movement shift the counters or drop the 12 o'clock counter.
- Day-date. The genuine window shows the day spelled out and the date in matching type. Copies mix fonts and use date wheels with wrong numeral sizes.
- Caseback. Genuine engraving is crisp and shallow with sharp edges. Copies cut deeper and softer.
- Crown and pushers. The 3717 has screw-down pushers. Many copies use push-in pushers.
- Coating. The real crystal shows a faint blue or purple tint. Cheap copies show none, or a heavy green cast.
- Magnet shield. Few copies fit the soft-iron inner case. A compass held to a genuine 3717 will swing. It stays still on most copies.
Legal status in the US
Trafficking in counterfeit goods is a federal crime under 18 U.S.C. 2320. A first offense carries up to 10 years, and repeat offenses up to 20 years. U.S. Customs and Border Protection seizes counterfeit watches at import and destroys the shipment. A buyer who imports a counterfeit loses the item and the money paid, with no refund from the seller.
What a reference number proves
A reference number names a model family. It does not identify one watch. Two watches with the same IW3717 code can differ in dial color, bracelet and market. Box, papers and service records carry more weight than the code in a listing title. If a seller cannot name the base calibre, the case size or the production years, the listing is a description, not a reference.