A fake IW371641 is a copy of the IWC Portugieser Chronograph in stainless steel. The real one is 41mm across, roughly 13mm thick, has no date, and runs IWC's in-house calibre 69355, a column-wheel chronograph visible through a sapphire caseback. Most fakes give themselves away on thickness first, then on the smaller details: subdial hand alignment, printed numerals, and what you find behind the display back.
What the real IW371641 actually is
Keep the target in your head before you look at anything. Steel case, 41mm diameter, leaf-shaped hands, bi-compax layout with running seconds at 6 o'clock and a 30-minute chronograph counter at 12. No date window on the dial. Sapphire crystal on both sides, 30m water resistance, and either an alligator strap or a steel bracelet depending on which version you are looking at.
Where fakes show themselves
Thickness and case profile
Measure the case with calipers if you can, or ask the seller for a photo against a ruler. Replica cases often come in at 13.5mm to 14.5mm because the movement inside is thicker than the 69355. Lugs on a copy tend to look a touch chunkier, and the polished and brushed surfaces meet in the wrong places. On the real watch the bezel is thin and flat, and the mid-case sits low.
Dial printing and subdial alignment
The 12 and 6 numerals are printed flat, not applied, and the baton indices are applied and polished. On a fake, the print is often slightly fuzzy under magnification, the numerals sit a hair off-center, and the subdial rings look shallow instead of snailed.
Run the chronograph. Start it, let it run, then reset. Both subdial hands should snap back to zero and point straight up at 12. A hand that lands at 11:58 or 12:02 is a bad sign, and so is a seconds hand that stutters.
The movement and the caseback
Look through the back. A real 69355 shows a column wheel, clean finishing, and a rotor with IWC engraving. Cheap fakes hide a Valjoux 7750 base under a decorated plate, which means the subdial layout is wrong and the pushers feel spongy. Caseback engraving should be crisp: reference, case number, and the maker's name all consistent with the paperwork.
Crown, pushers and feel
The crown is signed and winds smoothly. Pushers on a column-wheel chrono have a light, defined click. If the start pusher needs a hard shove or the reset grinds, you are not holding a 69355.
Price floor and paperwork
Used steel Portugieser Chronographs trade well into four figures. If someone offers an IW371641 for a few hundred dollars, it is a replica, no matter how good the photos look. Ask for the warranty card, the serial, and service history, then check the serial against the caseback.
Quick checklist
- Case measures 41mm, not 39mm or 42mm.
- No date aperture anywhere on the dial.
- Subdial hands reset dead vertical at 12.
- Printed 12 and 6, applied baton indices, sharp edges.
- Column wheel and engraved rotor through the caseback.
- Pushers click cleanly, crown winds without grit.
- Serial and reference match the card.
- Price sits in the normal used range for the reference.
What even the best replicas still miss
Top-tier copies get the dial color and the general silhouette close. They struggle with the caseback interior, the exact hand length and shape, the crispness of the printing under a loupe, and the chronograph feel. Those four things are where I spend my time when a watch shows up without a paper trail.
Buying used without getting burned
Buy the seller as much as the watch. Meet at a watchmaker if you can, have the movement photographed, and insist on a return window. If the seller refuses an inspection, that answers the question for you.