Short answer
A fake IW371470 is any watch sold as an IWC Portuguese Chronograph reference 371470 that was not produced by IWC Schaffhausen. The reference sits in the 3714 Portuguese Chronograph family, so a counterfeit usually copies a two-register dial, a slim steel case, and a Valjoux-based chronograph movement. Some copies are crude, running a battery quartz module behind a closed caseback. Others are built to a much higher standard and pass a casual glance. The checks below separate the two.
What the genuine reference looks like
The Portuguese Chronograph in this family uses a stainless steel case of roughly 40.9 mm across and about 12.3 mm thick, with a domed sapphire crystal. The dial carries two subdials, running seconds at 6 o'clock and chronograph minutes at 12 o'clock, and no date window. The movement is a chronograph caliber in the 79000 series, derived from the Valjoux 7750 architecture and running at 28,800 vibrations per hour. Confirm exact figures for your specific variant against IWC's own reference data before you compare.
Checks that expose a fake
- Measure the case with calipers at the widest point and across the caseback. A reading outside the published diameter by more than a fraction of a millimeter is a warning sign.
- Study the subdial positions. On the real dial they sit on a clean vertical axis at 12 and 6, and the spacing around them is even. Copies often shift one subdial a hair off center.
- Look for a date aperture. The reference has none. Any window at 3 o'clock means the watch is not built to this specification.
- Inspect the applied markers and hands under a loupe. Edges should be sharp and gold-toned metal should sit flush. Glue bleed, fuzzy printing, or wobbly numerals point to a low-grade copy.
- Run the chronograph. Start, stop, and reset the pushers several times. A genuine column-free cam system snaps back to zero in one clean motion. A cheap module hesitates or drags.
- Check the winding feel. A Valjoux-based automatic winds with light, even resistance. Gritty or stiff winding suggests a substituted movement.
- Verify the caseback engraving. Reference and serial numbers should be crisp, correctly spaced, and consistent with the case metal.
- Weigh the watch on a gram scale with the strap removed. Stripped-down copies are usually noticeably lighter because of thinner case walls.
Red flags in a listing
- A price far below the current secondary market range for the reference.
- Photos that avoid the caseback, the crown side, or the clasp.
- No movement photo, or a photo that shows a decorated plate bolted over an unrelated module.
- A seller who will not answer a direct question about the reference number stamped on the caseback.
- Paperwork that uses generic language instead of the correct reference and caliber.
Before you buy
Decide what you are actually shopping for. If you want an IWC, budget for the real secondary market price and insist on an independent inspection by a watchmaker who can open the case and read the movement. If you are deliberately buying a replica, treat the purchase as a replica purchase, ask for macro photos of the dial and movement, and confirm the return policy in writing. Mixing the two categories is where buyers lose money.