Short answer
The IW371488 is a reference in the IWC Portugieser Chronograph line. A fake IW371488 is a replica built to copy the outside of that watch. It gets the case shape and the two-register dial close. It misses the movement, the beat rate, the engraving, and the weight.
What the reference is
The Portugieser Chronograph uses a 40.9 mm stainless steel case, sapphire crystals, and a dial with the chronograph minutes at 12 o'clock and the running seconds at 6 o'clock. There is no date window. The steel version sits on a leather strap or a steel bracelet. Inside is the calibre 79350, an automatic movement built on the Valjoux 7750, with 31 jewels and a power reserve near 44 hours. US retail for steel models runs between about $7,000 and $8,500 by year and dial. IWC does not publish a separate page for every dial variant, so confirm the digits on the caseback before you buy.
What fakes get wrong
- Movement: quartz or a hand-wound Seagull ST19 instead of the automatic 79350. A rotor that does not turn, or that rattles, is a flag.
- Beat rate: the 79350 runs at 28,800 vibrations per hour, or 8 beats per second. Many replicas run at 21,600 vph, or 6 beats per second. Film the seconds hand in slow motion.
- Subdial spacing: the two registers sit too far apart, or pressed too near the center.
- Font: the IWC letters and the Schaffhausen text carry the wrong stroke weight and spacing.
- Crystal: weak anti-reflective coating. Real sapphire shows almost no reflection under a desk lamp.
- Caseback: shallow engraving, wrong reference digits, missing serial number.
- Weight: a steel 40.9 mm head on a leather strap runs about 75 to 90 grams. Copies land 15 grams or more off that range.
Checks you can run in a shop
- Ask for the reference and serial. Compare both against an IWC archive extract.
- Zero the chronograph. The minute counter at 12 must land on the marker, not drift.
- Press reset. A 7750 base resets with one firm click. A soft or grinding reset points to a copy.
- Wind 30 turns. The rotor should move with no rattle and no scraping sound.
- Ask about service history. US service centers will not work on a replica and will tell you so.
Price signals
Pre-owned steel Portugieser Chronographs trade in the $4,500 to $6,500 range. A listing at $400 to $900 is a replica. No legitimate seller moves a new IW371488 at that price.
Papers and box
Real sets include a warranty card with the reference and serial, a manual, and a box with the IWC logo stamped in the lining. Replica sets copy the look of the paperwork. Check that the serial on the card matches the serial engraved on the caseback. A mismatch is the end of the deal.