Short answer
A counterfeit IW371410 fails on three points: case size, dial printing and movement finish. The genuine IWC Portugieser Chronograph in this reference uses a 40.9 mm steel case about 12.3 mm thick, with a calibre 79350 automatic chronograph movement inside. Measure the case, loupe the dial text and the subdial hands, then check the rotor engraving through the case back. If any one of those checks fails, the watch is not genuine.
What the IW371410 should be
The IW371410 sits inside the IWC Portugieser Chronograph family. It has a stainless steel case, applied hour markers, two subdials and a case back that varies by production year. The dial carries the IWC and SCHAFFHAUSEN signature above the 12 o'clock subdial. That upper subdial counts chronograph minutes. The lower subdial runs the seconds. Reference numbers in this family begin with 3714, which is why sellers shorten the name to the 3714.
Counterfeit versions of this reference exist in several grades, from basic replicas to so-called 1:1 builds. The better fakes copy the outside of the case with real accuracy. They still give themselves away in the movement, in the dial printing and in the feel of the pushers.
Before you start
- A 10x jeweler's loupe
- Digital calipers that read to 0.01 mm
- A postal scale that reads grams
- Bright overhead light and a phone camera for close-ups
- The IWC published specification sheet for the reference, printed or on screen
How to check whether an IW371410 is fake
- Find the reference number engraved on the case back or between the lugs and compare it against the IWC published data for IW371410.
- Measure the case across the bezel at 3 and 9 o'clock with calipers. The genuine diameter is 40.9 mm, and a difference of 0.3 mm or more is a bad sign.
- Measure the thickness from the back of the case to the top of the crystal. Expect about 12.3 mm.
- Weigh the watch head on the postal scale and compare the figure against a known genuine example of the same reference.
- Study the dial text at 10x. On a genuine dial the IWC and SCHAFFHAUSEN lettering sits level, sits sharp, and has a matte finish rather than a glossy one.
- Check the applied hour markers. They should sit flat on the dial with no tilt and no visible glue at the base.
- Look at the subdial hands. On the genuine watch they reach the printed track and end cleanly.
- Pull the crown and set the time. The hacking seconds should stop, and the crown should click through its positions with a firm detent.
- Run the chronograph. Start it, stop it, reset it. The pushers should feel firm, and the center hand should snap back to zero with no bounce.
- Turn the watch over. If the case back has a display window, inspect the rotor engraving, the Geneva stripes and the blued screws under the loupe.
- Take the watch to an IWC authorized service center or a qualified watchmaker and have the case opened for a movement and serial number check.
Red flags
- Case diameter or thickness outside the published figures
- Dial text that sits low, runs uneven, or shines under light
- Subdial hands that stop short of the printed track
- A chronograph hand that bounces or fails to return to zero
- Rotor lettering that looks printed instead of cut into the metal
- A serial number that does not match the card, or that appears on other listings
- Spongy pushers or a crown that grinds when you turn it
When to get a second opinion
The best fakes of this reference copy the case well enough to fool a photo check. A movement inspection is the only test that settles the question. Budget for that service before you buy, and treat any seller who refuses to allow it as a reason to walk away.