Quick answer

A "fake IW371421" is a counterfeit copy of the IWC Portugieser Chronograph reference IW371421. The genuine watch is a 40.9 mm chronograph from the 3714 generation, running IWC calibre 79350, with small seconds at 6 o'clock, elapsed minutes at 12, a solid caseback, and a price that sat in the mid four figures when it was current. Copies of it sell for roughly 5 to 10 percent of that. On a table, a good copy can survive a glance. It does not survive a loupe and a winding rotor, and that is where I would start.

One thing worth knowing before you compare anything: the 3714 line is discontinued. IWC replaced it with a 41 mm Portugieser Chronograph using an in-house calibre, so a genuine IW371421 is a second-hand watch. Anyone selling you a "new" one from an authorised dealer is describing something that does not exist.

What the reference actually is

The IW371421 sits inside the 3714 family, a long run of 40.9 mm Portugieser Chronographs about 12 mm thick and rated to 3 bar. The reference suffix is what pins down the metal, dial colour, and strap, so two watches can share a case and movement while looking nothing alike. Most 3714 references are stainless steel; a few are precious metal. If you are verifying a specific piece, check the full reference against IWC's own records rather than trusting a seller's description or a forum post, because the suffix is the part people get wrong most often.

The proportions are the giveaway at arm's length. It is a slim, wide watch with a narrow bezel, so the dial dominates. Copies tend to be a touch thicker or a touch smaller, and the difference shows when you set it next to the real thing.

Start with the movement

Calibre 79350 is a reworked Valjoux 7750, and the 7750 leaves fingerprints you cannot easily hide. The rotor winds in one direction, so a genuine watch makes a soft whirr on one swing and a faint wobble on the return. That wobble is produced by the oscillating weight, and cheap copies either run a plain 7750 clone with the push and pull in different places, or run a quartz movement behind a decorative plate. If the second hand ticks in one-second jumps, stop there.

Then use the pushers. On a healthy 79350 the start press is crisp, the chronograph sweep is smooth, and the reset snaps back to zero in a single motion. Copies feel mushy, and the reset often drifts or needs a second press. Push the chronograph a few times before you buy and watch where the hand lands.

Case, crystal, and caseback

The 3714 generation has a solid caseback. That is the single most useful fact in this whole guide: if a seller shows you an IW371421 with a sapphire display back and a decorated movement visible, you are almost certainly looking at a copy, or at a different reference.

• Engraving depth. Genuine caseback text is cut cleanly with sharp edges. Copies are laser-etched shallow, and the letters look printed rather than carved.
• Finishing breaks. Look at the line between polished and brushed surfaces on the lugs. On the real watch it is a single crisp transition. Copies blur it or put it in the wrong place.
• Crystal. Sapphire with an anti-reflective coating shows a faint blue or violet flash at an angle. A flat, colourless crystal with no tint is a warning sign. Fakes often use mineral glass, which scratches and sounds dull when tapped.
• Crown and pushers. They should feel tight, with no lateral play, and sit flush against the case.

Dial, hands, and printing

I hold a loupe to the minute track first. On the genuine dial the hash marks are sharp and evenly spaced, printed with clean edges. Copies bleed slightly and the spacing drifts, usually somewhere around 4 and 8 o'clock where it is hardest to notice.

The applied numerals should be faceted and polished, standing proud of the dial with a visible edge. Stamped flat markers sit level with the surface and catch light differently. Hands should be polished on the top facet and matte or brushed on the side, which is a detail most copies skip. Subdial rings should be visibly recessed, and the snailing or texturing inside them should be fine and even.

Check the text at 12 and 6 under magnification. Letters should be crisp and consistent in weight. Blurry or thick printing is common on copies.

Strap, buckle, and paperwork

IWC ships these on signed alligator with a steel pin buckle. On the genuine strap the stitching is even, the leather edge is finished, and the buckle engraving is deep. Copies use embossed leather with shallow, rounded lettering on the buckle.

Papers matter less than the case number. The number engraved on the caseback should match the number on the certificate, and both should be traceable through IWC. A watch with a mismatched or missing number is a problem regardless of how good the dial looks.

What replica factories get right

Being honest about this helps. Top-tier factories do get the case dimensions, dial layout, and overall silhouette close, and at three feet in a dim room you might not pick one out. What they do not replicate is the movement, the depth and crispness of the engraving, the AR coating, and the tactile feel of the pushers. Those four things cost money, and they are what separates the categories.

If you are the one buying

Decide what you want first. A replica delivers the look and the wrist presence, and if that is your goal, buy from a seller who photographs the actual piece and states the movement honestly. If your goal is the real thing, buy from a dealer with service history, verify the reference suffix, and budget for a service on a discontinued 79350, since parts for a 7750 base are still plentiful but a watchmaker still has to open it. Either way, look at the caseback, listen to the rotor, and press the pushers. Those three checks settle most questions in under a minute.