The short answer
A fake IW371480 is only worth your money if the chronograph works like the real one. That means a Valjoux 7750 style automatic with three live functions: a 30 minute counter at 12, running seconds at 9, and a 12 hour counter at 6, with day and date sharing the window at 3. If a subdial is frozen, or the 6 o'clock register is a decorative disc glued to the dial, you are holding a sixty dollar watch with a three hundred dollar price tag. Everything else, dial print, case finish, strap, comes second to that single test.
Why this reference is easier to fake than most
The genuine Portofino Chronograph runs on IWC calibre 79320, which is a reworked Valjoux 7750. That matters, because the 7750 places its subdials at 12, 6 and 9, exactly where IWC put them. A replica builder does not have to invent a layout or hide a mismatched movement, which is why the movement is rarely the giveaway on a decent copy.
The flip side is that almost anyone can drop in a 7750 clone and call it a day. So the tells move elsewhere: the case proportions, the dial printing, and how carefully the movement was finished and cased.
What I check first, on the wrist
- Chronograph truth test. Start it. The 12 o'clock hand should sweep in 30 minute steps, the 6 o'clock hand should count hours. Reset hard. Both should snap to zero without drifting.
- Case thickness. Genuine is about 13.5mm. A 7750 based copy lands close. If it measures 15mm or more, a spacer is probably stacked over a thicker movement.
- Diameter. 42mm across, crown excluded. Listings quoting 44mm are selling a different watch with Portofino print on the dial.
- Day and date. Both in one window at 3, English day disc, clean printing. Fuzzy or off-center discs are the most common flaw in this reference.
- Pusher feel. The 7750 has a firm mechanical click. Mushy pushers, or a crown that will not thread, point to a cheap case.
Dial and case details that separate the tiers
Get a loupe on the printing. The IWC logo and Schaffhausen text should be thin and sharp. A lot of replicas lay the ink on too heavy and the letters blob together. Applied indices should sit flush with even lume fill. The bezel is polished, the case flanks are brushed, and the border between the two finishes should be a clean line, not a smeared transition.
Crystal: domed sapphire with anti-reflective coating on both faces. Outside-only AR leaves a blue or purple sheen. Genuine looks close to invisible from an angle. Caseback engraving should be deep and even, with the reference and calibre text in the right font weight.
Then the strap. Most copies ship with stiff embossed leather that ruins the whole thing. Budget for a replacement. A decent alligator grained strap changes this watch more than any other eighty dollars you can spend on it.
Movement, price, honest expectations
No superclone movement exists for this reference. The better versions run an A7750 or a decorated equivalent, and a sound example lands somewhere around $280 to $500 depending on case and dial grade. Past that you are buying a strap or a box, not a better watch. Under $200 you are usually looking at quartz with dummy subdials, or a 7750 with a dead 12 hour counter.
One quirk worth knowing: the 7750 is rotor heavy. A slight wobble on the wrist is normal, and so is rotor noise. Greasing it quiet is a bad trade.
Quick checklist before you pay
- Ask for video of the chrono running and resetting to zero.
- Ask for a movement photo, or at least confirm the calibre in writing.
- Confirm 42mm wide and roughly 13.5mm thick.
- Confirm the day disc is English.
- Confirm sapphire, not mineral glass.
- Treat any water resistance claim as marketing. Do not swim in it.