What the number means

IWC reference numbers carry six digits. The first four digits name the model line. The last two digits mark the dial and strap variant. Ref. IW3717 is the Pilot's Watch Chronograph Automatic. Known variants in that family include IW371701 and IW371704. I found no factory record for an IW371780 variant. A seller who quotes that exact number should show the caseback engraving and the warranty card before any payment.

Specs of the real 3717

  • Case: 42 mm stainless steel
  • Movement: caliber 79320, automatic
  • Frequency: 28,800 vibrations per hour, 25 jewels
  • Power reserve: 44 hours
  • Base architecture: Valjoux 7750
  • Crystal: sapphire with antireflective coating on both faces
  • Water resistance: 6 bar
  • Magnetic shielding: soft-iron inner case
  • Day and date window at 3 o'clock
  • Production run: 2006 to 2012, replaced by ref. 3777

Fake tells

Copies of the 3717 appear on auction sites and social media. Most fail on the same points.

  • Movement. A copy runs an unbranded 7750 clone or a quartz module. A real 79320 rotor carries the IWC name and the caliber number in engraving.
  • Day and date discs. On the 79320 the day disc sits above the date disc. Copies stack them in the wrong order or use a wrong numeral font.
  • Subdial layout. The 7750 places the three counters at 12, 6, and 9. A copy with a quartz movement puts them at other angles.
  • Dial print. Check the words "International Watch Co" and "Schaffhausen". Letters on a copy run thicker and sit closer to the dial edge.
  • Caseback. A real caseback carries the reference, the serial, a sapphire display window, and crisp engraving. Copies use shallow stamps.
  • Weight. The soft-iron inner case adds mass. Weigh the watch head and compare it to a documented example.
  • Pushers. Pushers on the 79320 need one firm press and reset to zero. Pushers that stick or need two presses point to a copy.

Checks to run before you buy

  1. Ask for a photo of the caseback with the reference and serial in focus.
  2. Ask for a photo of the movement through the display back.
  3. Time the chronograph against a stopwatch for 60 minutes.
  4. Measure the case with calipers. A 42 mm case reads 42.0 mm at the bezel edge.
  5. Look at the crystal under a phone light at a shallow angle. Two-sided antireflective coating shows a faint blue tint.
  6. Compare the asking price with sold listings for ref. 3717. A price below the market range points to a copy.

Bottom line

A fake IW371780 fails on the movement first. Request movement photos and caseback photos. Confirm the reference digits against IWC records. If the seller cannot supply both photos, stop the deal.