What "fake IW371665" means
IW371665 is a reference number from IWC Schaffhausen. A fake IW371665 is a watch built by a third party that carries that number and the IWC name without permission from IWC. Sellers use the number because it points to one catalog model, not a general style.
The real reference
The number sits in the IW3716xx block, which covers Portugieser Chronograph models. IWC publishes case size, calibre, dial color and strap for each reference on its own site. Read that page before you compare any watch to a copy.
IWC has changed movements inside this family. Older Portugieser Chronograph models used calibre 79350, a modified Valjoux 7750 base. The 41 mm chronograph released in 2020 uses calibre 69355, a column wheel chronograph with a 46 hour power reserve. A spec sheet from a seller is not a source for this data.
Price gap
A steel Portugieser Chronograph lists near $8,000 on IWC's site. Gold versions cost several times more. Copies sell from $200 to $700. That gap is why the search term exists. It also describes what the copy is not: no in-house movement, no precious metal, no IWC service history.
US law
Importing, selling or trafficking counterfeit watches is a federal crime under 18 U.S.C. § 2320. A first offense carries up to 10 years in prison and a $2 million fine for an individual. Customs and Border Protection seizes counterfeit goods at ports and destroys them. A buyer who imports a fake watch can lose the item and the money paid for it. Reselling one adds trafficking exposure. A trademark holder can also sue under the Lanham Act.
How copies fail inspection
- Movement. Copies use unbranded Valjoux 7750 clones, Seagull ST19 hand wound calibres, or quartz in cheap builds. Subdial spacing shifts when the wrong movement goes in.
- Caseback. Engraving depth, font and reference spacing differ. Serial numbers on copies repeat across many units.
- Dial. The IWC wordmark and printed indices lose crispness at the edges. Lume plots sit off center.
- Chronograph. Pusher travel and reset snap feel different from calibre 69355.
- Papers. Box, booklet and warranty card print quality. The card serial must match the case serial.
- Weight. Case metal and movement mass add up. A kitchen scale against published specs finds the thin ones.
Service and resale
IWC service centers do not service counterfeit watches. Some confiscate them. A copy has no dealer resale value. Authentication by an independent watchmaker costs money and needs the watch in hand, not photos.
Checks before payment
- Confirm the reference on iwc.com.
- Ask for photos of the caseback serial and the paperwork serial.
- Have a watchmaker open the caseback and photograph the movement.
- Weigh the watch and compare to published specs.
- Meet at an authorized dealer or service center when you can.
What no page can confirm
IWC does not publish a public authentication database. Listing data for IW371665 changes over time. Any claim that a single online checker verifies this reference is not supported by a primary source.