Short answer
A fake IW371654 is a copy of the IWC Portugieser Chronograph sold as the real watch. IW371654 is one reference inside the Portugieser Chronograph line. The reference number stamped on a caseback proves nothing, since replica makers print correct numbers. Authentication rests on the movement, the case finishing, and the papers.
What the genuine reference should show
IWC builds the Portugieser Chronograph around a 41 mm steel case and calibre 69355, an in-house automatic chronograph with a column wheel and a 46-hour power reserve. The case has a sapphire display back. Water resistance is 30 m. The dial carries two subdials: running seconds at 6 o'clock and chronograph minutes at 12. The date sits at 3.
Dial colour, strap, and production year change with the reference and the batch. Confirm the exact variant against an IWC catalogue or an authorized dealer before you judge a watch.
Start with the movement
The display back is your best test. On a genuine calibre 69355 you see a column wheel in the chrono works, Geneva stripes on the bridges, circular graining on the base plate, and a signed rotor with the calibre number.
Replicas of this watch usually carry a Valjoux 7750 base or a Chinese clone. Those movements use a cam and lever, not a column wheel. Look at the rotor text: laser etching sits on the surface with a flat grey tone, while genuine engraving cuts into the metal. Check the balance cock shape, the jewel count, and the pusher position against the movement.
Case, dial, and bracelet checks
- Case thickness. The genuine case is about 13 mm. A thin or thick case points to a copy.
- Lugs. Crisp bevels and even polishing. Replica lugs show rounded edges and soft transitions.
- Dial print. Text should stay sharp under a loupe. Fakes show thick strokes and merged letters.
- Subdial rings. Genuine subdials carry fine concentric snailing.
- Hands. Leaf shaped, with clean edges and flat surfaces.
- Date window. Square cut, frame aligned to the dial.
- Crown. Signed, with sharp relief.
- Clasp. Engraving depth and spring bar fit.
Photograph the watch in daylight and compare the images with IWC press photos. Shadows hide soft edges.
Caseback, serial, and papers
Reference and serial numbers sit between the lugs and on the caseback rim. Depth and font matter. Shallow laser marking with a dot matrix look is a warning sign. IWC keeps no public serial lookup, so a number check needs IWC service or an independent watchmaker.
Papers count as much as the watch. Ask for the warranty card, booklet, and box. Match the card date to the reference and to the serial. A card printed with the wrong reference is a frequent replica error.
Price and seller signals
Steel Portugieser Chronograph watches trade on the secondary market at about $4,000 to $8,000 USD, with box and papers adding a premium. An offer far below that range is a flag. So is a seller who refuses macro photos of the movement, or who ships from a country the listing does not state.
What to ask before you pay
- Macro photos of the dial, caseback, movement, and clasp.
- The full serial and reference, in writing.
- Service history and the name of the watchmaker.
- A return window in writing.
Take the watch to a watchmaker with a timing machine. Calibre 69355 runs at 28,800 vph and starts clean. A clone shows a wide amplitude spread and a rough chrono start. If you cannot inspect the watch in person, buy from a seller with a documented return policy.