A fake IW371740 is an unauthorized copy of IWC's Pilot's Watch Chronograph reference IW3717, a 42 mm steel chronograph produced from roughly 2006 to 2012 on the modified Valjoux 7750 calibre 79320. The fastest tells are the soft-iron inner case, the crispness of the caseback engraving, and the day-date font at 3 o'clock. Genuine watches carry a reference and serial number that IWC can verify, while copies reuse a small set of numbers.
What is the IW371740 reference?
IW371740 sits inside the IW3717 block, the reference family IWC used for the 42 mm Pilot's Watch Chronograph Automatic. That watch has a black dial with large white numerals, a day-date window at 3 o'clock, and a chronograph driven by calibre 79320.
IWC issued the block in several dial, case, and strap variants, so the trailing digits change the finish rather than the platform. A listing that pairs the IW371740 number with 43 mm dimensions is describing the 2012 successor, the IW3777 family.
How do you spot a fake IW371740?
- Caseback engraving. Genuine engraving is deep and even, with fine lettering and a correct reference and serial. Copies show shallow laser etching, thick letters, and numbers that do not match the dial variant.
- Soft-iron inner case. IWC shields this pilot's watch with a soft-iron cage that adds measurable weight and magnetic resistance. Copies omit it, so the watch feels light and runs fast near magnets.
- Dial printing and lume. Genuine numerals and the minute track are sharp, and the lume sits in even, flat coats. Replicas show fuzzy edges, uneven lume, and slightly wrong spacing in the IWC and Schaffhausen text.
- Crown and pushers. The screw-down crown threads smoothly and the pushers have a short, crisp travel with a firm reset. Copies feel gritty or spongy and often use a crown with the wrong profile.
- Crystal. The 3717 uses convex sapphire with an inner anti-reflective coating that reads almost colorless. Copies use flat mineral glass or coated sapphire with a strong blue or purple tint.
Where do replicas slip on the movement?
Calibre 79320 is a 25-jewel automatic chronograph that beats at 28,800 vibrations per hour, and IWC finishes the rotor and bridges above the standard 7750 layout. Most copies hide an unbranded 7750 clone or a low-grade chronograph module behind the caseback.
The 3717 has a solid steel caseback, so the movement is never visible from outside. Any seller who shows a "movement photo" of an IW371740 is photographing a different watch.
Does the day-date window give a fake away?
The genuine 3717 uses a single-language day wheel with a specific sans-serif font, and the two discs sit level in the aperture. Replicas often show a bilingual day wheel, a smaller or bolder font, or discs that sit at different depths.
Can you verify the serial number?
IWC does not publish a public serial database, so a search box cannot confirm authenticity. The practical route is to send photos of the caseback, dial, and papers to IWC service or an authorized dealer and ask for a check against their records.
What are the legal and practical risks?
Counterfeit watches are subject to seizure at the U.S. border, and importing them can bring civil penalties. Selling a copy as a genuine IW371740 is fraud, and the buyer gets no warranty, no service support, and almost no resale value.
A qualified watchmaker can settle the question in minutes by opening the case and checking the movement, the cage, and the caseback stamps.
What should you confirm before you buy?
- Case size, reference, and serial all match the IW3717 specification.
- Weight and magnetic behavior are consistent with a soft-iron inner case.
- The day-date font, dial printing, and lume look factory crisp.
- The seller can document service history or a brand verification.