A fake IW371670 usually fails on four checks: case thickness, the movement visible through the exhibition caseback, the crispness of the dial printing and applied numerals, and the feel of the crown and chronograph pushers. Genuine watches in this IWC Portugieser Chronograph family run the in-house calibre 69355, a column-wheel chronograph that no budget counterfeit reproduces accurately. If any one of those four points looks wrong, treat the watch as suspect until a watchmaker opens it.
What gives away a fake IW371670 fastest?
The case profile gives it away first. A genuine Portugieser Chronograph in this reference family measures roughly 41 mm across and about 13 mm thick, while most counterfeits add 1 to 2 mm because the generic movement inside sits taller. Lay the watch flat next to a ruler and compare before you look at anything else.
How do you check the movement?
Genuine IW3716 references have a sapphire exhibition caseback, so the calibre 69355 is visible without opening the watch. Look for the column wheel, Cotes de Geneve striping, blued screws, and the engraved Probus Scafusia rotor medallion. Counterfeits typically show a Seagull ST19, a Valjoux 7750 clone, or a decorated plate over a quartz module, none of which match the genuine architecture.
What are the dial and case tells?
- Subdials: genuine bi-compax layout with running seconds at 6 and chronograph minutes at 12, date at 3, spacing tight and even.
- Printing: sharp, level text with no bleeding and correctly proportioned IWC and Schaffhausen lettering.
- Numerals: applied and polished, seated flat; fakes often sit high or reflect light unevenly.
- Pushers: firm with a clean start, stop, and reset; counterfeits feel gritty or spongy.
- Crystal: strong anti-reflective coating, so the dial reads almost black at shallow viewing angles.
What should the caseback and paperwork show?
Engraving on genuine casebacks is deep, crisp, and evenly spaced, with the reference and serial numbers matching the warranty card and IWC service records. Blurry laser etching, mismatched numbers, or misplaced Swiss Made text are common giveaways on counterfeits. Ask for a service invoice or an archive extract when buying secondhand.
Is a replica IW371670 worth buying?
No replica of this reference reproduces the calibre 69355, so any IW371670 replica is a different watch with different servicing, reliability, and resale behavior. What you get is a cosmetic copy of the dial and case, sometimes with a working chronograph movement and sometimes not. Price it as a fashion watch, not as a collectible.
Quick checklist before you pay
- Measure case thickness and compare it with the official specification.
- Look through the caseback and identify the movement layout.
- Inspect dial printing and applied numerals with a loupe or phone macro lens.
- Match reference and serial numbers across watch, card, and box.
- Have a watchmaker time the movement and confirm amplitude and rate.