Short answer
A fake Portofino 42 is graded on four points: case size, dial layout, chronograph function, and caseback finish. A strong replica copies the genuine 42 mm Portofino Chronograph case, keeps the counters at 12 and 6 o'clock, and runs a chronograph movement that resets to zero. A weak one misses at least one of those points, and you can spot the miss in about a minute with a caliper and a loupe.
What you need before you compare
- The exact reference you are matching. IWC built the Portofino Chronograph with several dial colors, strap options, and date or day-date windows.
- Factory numbers for the 42 mm case: about 42 mm wide, about 13.5 mm thick, 20 mm lugs.
- A digital caliper, a 10x loupe, and a kitchen scale that reads in grams.
- Front, side, and caseback photos of the genuine watch open on a second screen.
How to check a fake Portofino 42
- Measure the case width across the bezel at the 3 and 9 o'clock points with a digital caliper.
- Measure the thickness from the caseback to the top of the crystal.
- Check the lug width at the spring bar gap. It should read 20 mm.
- Compare the subdial positions to a photo of the genuine dial. The counters sit at 12 and 6 o'clock.
- Inspect the day and date window at 3 o'clock. Look at the cut, the frame, and the font of the numerals.
- Study the hands and applied markers under the loupe. Genuine hands have beveled edges and a clean polish line.
- Run the chronograph five times. Start it, stop it, and reset it, then watch whether the hand snaps back to 12 or drifts.
- Read the caseback with the loupe and compare the reference number and engraving depth to the factory photos.
- Weigh the head and flex the strap, then check the clasp engraving for depth.
Movement tells
Most Portofino 42 replicas use a modified Valjoux 7750 style movement or a quartz module. The 7750 layout puts three counters on the dial, and the genuine Portofino uses two, so makers hide the third counter behind a printed or blanked subdial at 9 o'clock. Look at that area under raking light. If you can see a faint circle, a screw, or an uneven finish, the dial was built around a stock movement. A quartz version gives itself away with a ticking running seconds hand on the subdial at 6.
Buying Guide: Fake Portofino 42 Watch
Where cheap versions fail
Low end replicas tend to get the case size close and everything else wrong. The common failures are a case that reads 43 mm or more on the caliper, subdials that sit too close to the center, a pusher that feels mushy, a crown with rough knurling, and a caseback engraving that looks printed instead of stamped. Strap quality is the fastest tell on a leather model, since the fake alligator is usually embossed cowhide with a plastic sheen.
Which details matter most
If you only check one thing, check the dial layout. Case size is easy for any factory to copy, but subdial spacing, print weight, and marker height take real tooling. Photograph the dial straight on with a phone at 2x zoom and lay it next to a genuine photo at the same scale. Misaligned counters and a date window that sits a hair too high or low show up fast in that comparison.