A genuine IW371642 is an IWC Portugieser Chronograph. A replica is a copy built to look like it. A fake is a counterfeit offered as an original. The fastest checks are the sub-dial layout, the caseback, and the movement behind it.
What the reference is
IW371642 sits in the Portugieser Chronograph family, reference 3716. IWC lists that family with a 40.9 mm steel case, a 30-minute chronograph counter at 12 o'clock, running seconds at 6 o'clock, a date at 3, and Calibre 69355 with a column wheel and a 46-hour power reserve. The exact dial and strap variant for IW371642 was not confirmed for this guide. Use the IWC reference lookup before you compare anything else. A wrong reference code in a listing is the first sign of a mismatched watch.
Check 1: sub-dials and pushers
Running seconds sit at 6. The 30-minute totalizer sits at 12. The date window sits at 3. Many replicas run an A7750 or a Seagull ST19 and shift the sub-dials, add a 12-hour counter, or drop the date. Look at the hands inside each sub-dial. On the original the small seconds hand sits close to the dial. On low-grade copies it floats above the surface. Press the pushers. A column wheel starts and stops with a short, clean click. A cam-and-lever copy feels soft, and the chrono hand stutters on start.
Check 2: caseback and movement
Reference 3716 ships with a sapphire display back. You can see the movement. Genuine Calibre 69355 shows striped bridges, a signed rotor, and perlage. A replica shows a decorated plate, a printed sticker, or a rotor with shallow engraving. A solid steel back on a 3716 is a warning sign. Ask for a clear photo of the movement and compare the bridge shape, not the engraving.
Fake IW371642 Copy: How to Judge One Before You Pay
Check 3: dial print and hands
The hands are leaf shaped. The numerals are applied. The printing is thin. On the original, the IWC mark at 12 is crisp and the minute track spacing is even around the full dial. Replicas show thick paint, uneven track spacing, and flat hands with no facet. Blued hands on steel models change tone with the light. Painted hands do not.
Check 4: case, crown, thickness
Measure the case with a caliper. Replicas often run 1 mm to 2 mm thicker because the substitute movement is taller. Check the crown engraving under a loupe. Check lug shape and bezel polish against a known genuine example. Weight is a rough guide only, since straps and bracelets change the total.
Check 5: papers, price, seller
A full set means box, booklet, warranty card, and a serial that matches the caseback. Ask for one photo that shows the card and the caseback together. Retail on a steel Portugieser Chronograph sits near $8,000 USD. Used prices move with age and condition. A price far under market is the oldest signal there is.
Legal position in the US
Trafficking in counterfeit watches violates 18 U.S.C. § 2320 and US trademark law. CBP seizes counterfeit goods at import. Buying a replica for personal wear is a separate question from selling one, and state rules differ. None of this turns a counterfeit into a collectible.
What a replica can and cannot do
A good replica gets the silhouette right. It does not get the movement right, and the movement holds most of the cost. Resale value on a replica is close to zero. Service is hard to source because parts do not match any catalog. If the goal is the look at low cost, buy with that in mind. If the goal is the watch, buy the watch.