The IW371431 is a reference in IWC's Portugieser Chronograph family, so "fake IW371431" questions almost always come down to one test: does the watch carry a genuine caliber 79350 and the case, dial, and paperwork details that belong with it? Real examples run a 40.9 mm case, a bi-compax dial with running seconds at 6 and a 30-minute counter at 12, and a sapphire display back showing a Valjoux 7750 based movement finished by IWC. Fakes fail on the movement, the subdial functions, the crystal coating, and the engravings, usually in that order.

What is the IWC IW371431?

The IW371431 belongs to the IW3714 generation of the Portugieser Chronograph, a steel-cased line that IWC produced for roughly two decades before replacing it in 2020. That generation used the caliber 79350, a 7750 base reworked by IWC, with a 44-hour power reserve and a 28,800 vph beat rate. The current Portugieser Chronograph uses the in-house caliber 69355, so any seller describing a brand-new IW371431 as fresh stock deserves a second look.

How do you spot a fake IW371431 quickly?

• Subdial functions: the 6 o'clock subdial must run continuously as seconds, and the 12 o'clock counter must jump in one-minute steps when the chronograph runs.
• Case thickness: genuine examples sit near 12.3 mm; many replicas add a millimeter or more and feel top-heavy on the wrist.
• Crystal: IWC coats both faces of the sapphire, which produces a faint blue-violet sheen and near-total glare control.
• Caseback: the reference and serial engravings are crisp, evenly spaced, and cut into the metal, not laser-printed on a flat surface.
• Dial printing: "SCHAFFHAUSEN" sits tight under the applied IWC logo, with no blurring at the edges of the letters.
• Papers: the warranty card, booklet, and serial numbers should match the watch and the box.

How do you check the movement in a suspected fake?

Ask for a clear photo of the movement through the caseback. A genuine 79350 shows a signed rotor with the Probus Scafusia medallion, brushed bridges with Geneva stripes, and blued screws seated flush. Aftermarket movements in fakes often show rough perlage, misaligned screw slots, and a rotor engraving that looks stamped rather than cut.

Why do the subdials matter more than the finish?

Most fake Portugieser chronographs run a stock 7750 layout, which puts running seconds at 9 and the chrono counter at 3. Watchmakers can re-route the dial train, but many budget fakes simply mirror the look and leave the functions wrong. Time the chronograph for a full minute and confirm the 12 o'clock hand advances exactly once.

What do the case and dial details reveal?

The genuine case is fully polished with sharply defined lug flanks, and the bezel edge catches light in one continuous line. Fake cases often show soft transitions, uneven polishing under the lugs, and a crown that sits slightly proud of the case band. On the dial, the applied numerals have beveled edges and the leaf hands are thin at the tips with a clean curve.

Are high-end replicas of the IW371431 convincing?

Top-tier replicas get the outside close, including the dial layout and the case proportions, so photos alone are not enough. The gap shows up in the movement, the crystal coating, the strap hardware, and the engraving depth. Buyers who handle a genuine example first rarely mistake a replica for the real thing in person.

What price should an IW371431 sell for?

Steel IW3714 chronographs traded around $7,000 to $8,000 at retail and now change hands on the secondary market for roughly $4,500 to $6,500 depending on condition and completeness. A listing far below that range, especially one with vague photos and no service history, is the strongest single warning sign. Ask for a timestamped photo set, the serial, and a return window in writing.

Is the IW371431 still in production?

No. IWC moved the Portugieser Chronograph to the in-house caliber 69355 in 2020, so the IW3714 references are discontinued. That makes full sets with original paperwork more valuable and makes "new old stock" claims worth verifying through an authorized service center.

Can IWC verify a serial number?

IWC boutiques and authorized service centers can confirm a reference and serial combination during a service intake, though there is no public online database. A seller who refuses to let a watch be checked at a service center is telling you something useful.