Short answer
IW371425 is an IWC reference number in the Portugieser Chronograph line. A watch sold under that number for a few hundred dollars is a counterfeit. Genuine IWC Portugieser Chronographs trade on the secondhand market in the low four figures and up. The reference number alone tells you little. The caseback, the movement and the dial do the work.
What the reference number covers
IWC reference numbers start with IW followed by six digits. The 3714 block covers the Portugieser Chronograph. IWC has changed specifications in this line more than once, and the same reference can appear with different dial colors across production years. Confirm the exact configuration with IWC before you compare photos. If a seller's spec sheet does not match IWC's records for that reference, stop there.
Price gap
- Counterfeit: $150 to $600, listed as "1:1" or "clone."
- Genuine, used: several thousand dollars, set by year, box and papers.
No seller moves a real IWC at a 90 percent discount.
Caseback and engraving
Genuine casebacks carry the reference number, the serial number, and "IWC Schaffhausen" in a stable typeface. On fakes the engraving is shallow, uneven, or laser-etched with sharp edges. Serial numbers on fakes repeat across units. Ask for the serial and the reference in one photo of the caseback.
Movement
IWC used calibre 79350, a modified Valjoux 7750, in older Portugieser Chronographs. Newer versions use the in-house calibre 69355. Both run at 4 Hz, or 28,800 beats per hour. A fake usually hides an unmodified 7750 clone or a quartz module. A quartz fake ticks the chronograph seconds hand once per second. A 7750-based watch advances it in small steps.
Dial and hands
Look at the printing. Genuine appliques and text sit level and centered. Fakes show off-center subdials, patchy lume, and hands that miss the markers at 12. The Portugieser Chronograph has two subdials, one at 12 o'clock and one at 6.
What fakes get right
Case size, dial layout and strap are close on the better fakes. Photos alone cannot confirm a watch. Open the caseback with a watchmaker, or send the watch to IWC for service authentication.
Limits
Specification details change by production year. Where a listing conflicts with IWC's published data, treat the listing as wrong until proven otherwise.