Short answer
When people search for a fake IW371756, they almost always mean a replica of the IWC Portugieser Chronograph. The reference belongs to that line: a stainless steel, two-register chronograph with a clean, wide dial. The digits after the base model number are IWC's code for the dial and strap combination, so a 371756 is not a different watch from its 3717xx siblings. Same case, same movement family, different finish. That matters for buyers, because replica makers copy the case shape well and the variant details badly.
The genuine watch in one paragraph
Steel case around 41mm across, roughly 13mm thick, sapphire crystal front and back, two subdials at 12 and 6, no date window on the classic version, leaf-shaped hands, applied numerals, a printed railway minute track, and an alligator strap with a signed buckle. Water resistance is modest, in the 3 bar range, because this is a dress chronograph and not a sports watch. Older production used a slim Jaeger-LeCoultre based calibre. Later production moved to a modified Valjoux 7750. Both are thin enough to keep the case under 14mm.
Where replicas fall apart
- Subdial spacing. This is the single biggest tell. Different base movements push the two registers to different distances from the centre, and a copy with the wrong spacing looks slightly cross-eyed once you notice it. Compare against a straight-on photo of the real thing.
- Case thickness. A 7750-derived clone is thicker than the original movement. Cheap builds end up near 15mm and sit high on the wrist. If the seller will not show a side profile on a measuring caliper, assume the worst.
- Dial printing. Genuine printing is crisp under magnification, with even weight on the numerals. Copies often show slightly fat text, a blurry minute track, or subdials that sit a fraction off centre.
- Hands. The leaf hands should be polished on the top facet and satin on the sides. Many replicas are fully polished and catch light in a way the original does not.
- Caseback engraving. Reference, serial, and Swiss Made marks are laser sharp on the real watch. On copies they are often shallow or slightly crooked, and the movement decoration behind the sapphire rarely matches the real finishing.
- Strap and buckle. Genuine straps carry a signed buckle with clean stamping. Replica straps tend to use soft, thin leather and a stamped buckle with rounded edges.
Movement: what is actually inside
Most fakes in this family run a Chinese copy of the Valjoux 7750. That is not automatically bad, since the genuine later production is also 7750-based. The difference shows in feel. A real 7750 winds with a light, even resistance. Clones often feel gritty or stiff, and the rotor can wobble audibly when you tilt the watch. Ask for a video of the watch being wound and shaken. A seller who refuses is hiding something.
Price tiers
Entry builds run a couple of hundred dollars and show it: wrong thickness, flat dial printing, hollow-sounding rotor. Mid tier gets the proportions closer and adds a decorated movement, but subdial spacing and hand finishing still slip. Top tier copies get the case profile, crystal height, and dial layout right, and they cost enough that you should ask yourself what you are actually buying. The gap between mid and top is mostly in the small things, and those small things are exactly what you stare at every day.
Red flags before you pay
- No macro photos of the dial and caseback.
- No movement photo, or a stock photo reused from another listing.
- Claims of "Swiss made" movement at a price that cannot support one.
- Thickness or weight quoted without a scale or caliper in frame.
- Pressure to pay outside any traceable method.
Legal reality
Counterfeit watches infringe registered trademarks, and customs agencies in the United States and the European Union seize them routinely, including single-piece personal orders. Importing a counterfeit is prohibited in the US even when it is for personal use. Know that before you order, and know that a seized parcel is money gone.