Short answer
Fake IW371433 watches are common enough that you should treat any secondhand Portugieser Chronograph at a bargain price as suspect until a watchmaker says otherwise. Three checks catch most of them: the caseback engraving and serial, the sharpness of the dial printing under magnification, and whether the chronograph hands snap back to zero at 12 and 6 without drifting. A genuine IW371433 also carries a movement that fills the display back properly, with a level of finishing that budget copies skip.
What the real IW371433 is
The reference belongs to IWC's Portugieser Chronograph 3714 family. Stainless steel case around 40.9 mm across, twin register dial with elapsed minutes at 12 and running seconds at 6, date at 3, leaf shaped hands, applied numerals, and a railway minute track around the outer edge. Inside sits IWC calibre 79350, built on the Valjoux 7750 architecture and reworked by IWC with its own gearing and finishing.
Because that calibre is a mass produced chronograph movement, cloning it is cheap. That single fact explains why the 3714 line gets faked far more often than IWC's in-house perpetual calendars.
Dial tells
The dial is where the money goes on a genuine watch, and where replicas cut first.
- Printing. "IWC Schaffhausen" should be razor sharp with consistent stroke weight. Copies look a little fuzzy, or one word sits heavier than the other.
- Minute track. The individual hash marks on a real dial are uniform in spacing and thickness. On fakes the spacing drifts near the subdials.
- Hands. Genuine leaf hands are faceted, with a polished bevel and a visible center line running the length of each hand. Most replicas are flat or rounded with no facet at all.
- Subdials. The snailed texture inside each register should be fine and consistent. Cheap versions print a flat pattern or leave the texture out.
- Date window. The aperture edge is cut clean and the number sits centered. A fake often shows a thick frame or a date that rides high in the window.
Movement and caseback
If the watch has a display back, ask for a movement photo before anything else. Genuine 79350 movements show striped or circular graining, a signed rotor, and proper screw heads. The engraving on the rotor is cut deep, not laser etched on the surface.
Then run the chronograph. Start it, let it run 30 seconds, stop it, reset it. The hands should snap back to zero and stay there. On a 7750 based movement the reset is crisp. If the chrono seconds hand parks a hair past the 12 marker, or the minutes counter creeps while the chronograph is stopped, walk away.
Case, weight, and feel
Measure the diameter. A watch sold as a 40.9 mm Portugieser that measures 42 or 43 mm is a different case, and no amount of good dial work fixes that. Check the lug profile too: brushing on top, polish on the bevel, a crisp line between the two. Replicas blur that transition or polish the whole lug.
Weight is a rough guide, not a test. A steel 3714 on a leather strap feels substantial in the hand, and the rotor swings with a soft click. A quartz fake feels hollow and has no rotor to swing.
What to pay, and what to skip
Two rules cover most situations.
- If the price is less than half of what the reference trades for on the used market, assume fake until proven otherwise.
- If the seller will not send a movement photo, a video of the chronograph running, and a clear shot of the caseback engraving, end the conversation.
On the replica side, tiers matter. The cheapest versions use quartz, or a 24 hour subdial dressed up to look like a chronograph. Mid tier copies run a working 7750 pattern movement with a rough finish and a case that is a millimeter or two off. The top tier, the ones sold as super clones, copy the case geometry, the sapphire, and the dial layout well enough that only a loupe or a caliper gives them away.
If you buy a fake, buy it as a fake and pay a fake price. If you buy genuine, buy from someone who will let a watchmaker open the case before money changes hands.