What a fake IW371789 is
A fake IW371789 is a counterfeit copy of an IWC Portugieser Chronograph sold under that reference number. The quickest way to catch one is to verify the reference before you look at anything else. Counterfeiters take a real reference number and put it on a watch with the wrong dial color, the wrong subdial spacing, or a case that is a fraction of a millimeter too thick. If the number on the caseback, the dial printing, and the seller's description do not line up with what IWC actually made under that reference, stop there. No photo of a movement makes up for a reference that does not exist in that configuration.
What to have before you inspect
- A digital caliper that reads to 0.01 mm
- A 10x jeweler's loupe
- A gram scale
- Photos of a known-genuine example of the same reference, from more than one angle
- The seller's photos of the caseback, the guarantee card, and the movement
How to check a suspect IW371789
- Ask the seller for a clear photo of the caseback engraving and the guarantee card, then confirm the reference, dial variant, and case metal match each other.
- Measure the case across the bezel at 9 to 3 with the caliper and note the number to two decimals.
- Measure the case thickness from the crystal top to the caseback center and write that number down next to the diameter.
- Compare both figures with the published specification for the reference, allowing for crystal dome height and normal production tolerance.
- Look at the subdials and confirm the layout: small seconds at 6 o'clock, chronograph minutes at 12, and a date window at 3.
- Check the gap between each subdial and the printed minute track, since replica dials often sit a little tight or a little wide.
- Read the dial text with the loupe and compare letter spacing, stroke weight, and the position of the printed signature against your reference photos.
- Start the chronograph, let it run for a full minute, stop it, and reset it, watching whether the central hand snaps back to zero and stays there.
- Press each pusher slowly and feel for slack, grinding, or a mushy stop before the mechanism engages.
- Unscrew and reseat the crown a few times and check that the threads engage smoothly without rocking.
- Turn the watch over and inspect the sapphire caseback, the engraving depth, and the finish on the movement bridges and screws.
- Weigh the watch head on the gram scale and then weigh it again with the strap or bracelet fitted, and compare both totals with your reference figures.
- Ask for the original invoice, service paperwork, and box, and check that the serial on the papers matches the serial on the caseback.
- Compare the asking price with the current secondary market for that reference and treat any figure far below it as a reason to walk away.
Red flags that settle it fast
- Subdials positioned at 3, 6, and 9 instead of 12 and 6
- Printed text that sits too close to the bezel edge
- A case that measures noticeably thicker than the published figure
- Rotor noise or a free-spinning rotor when the watch is tilted
- No serial number, or a serial that does not match the paperwork
- Seller who will not send a photo of the caseback at an angle
What replicas do get right
Modern copies handle the easy parts well. Case geometry at arm's length, the color of the dial, the shape of the leaf hands, and the feel of the strap are close enough to fool a buyer in a hurry. The faults show up in the details: engraving depth on the caseback, the finish of the movement, the crispness of the printed minute track, and the snap of the chronograph reset. Judge the watch on those, not on how it looks in a listing photo taken at an angle.