A fake IW371633 is any watch built to look like the IWC Portugieser Chronograph of that reference without being produced by IWC Schaffhausen. Most counterfeits give themselves away in four places: case proportions and finishing, dial printing and subdial layout, the movement seen through the case back, and the paperwork that travels with the watch. If two or more of those checks fail, treat the watch as a fake IW371633 and walk away.
What the IW371633 Reference Actually Is
The reference sits inside the IWC Portugieser Chronograph family, a two-register chronograph line with a clean minute track and two subdials. Because IWC has issued several dial colors, strap options, and small running updates inside the same block of references, the exact specification of the IW371633 matters. Pull up the official product page for that reference before comparing anything, then match dial color, hands, and case metal first. Details that belong to a different variant are a common reason people misjudge an authentic watch as a counterfeit.
Check 1: Case Dimensions, Shape, and Finishing
- Measure the case across the bezel without the crown and compare it to the published figure for the reference.
- Run a fingernail along the lug edges. Genuine lugs are polished on the top surface and brushed on the sides, with a crisp line between the two finishes.
- Look at the crystal edge. Sapphire should sit close to flush with the bezel and show little distortion at a shallow angle.
- Inspect the crown. It should be signed, wind and set smoothly, and sit against the case band without a visible gap.
Finishing is where budget counterfeits fail fastest. Blurry transitions, softened lug edges, and a bezel that reflects light unevenly all point to a case made for the replica trade rather than an IWC case.
Check 2: Dial Printing and Subdial Layout
- Text under 12 o'clock should stay sharp under magnification, with even stroke weight across every letter.
- The minute track should be printed cleanly, and every hash mark should be the same length.
- Chronograph subdial hands should reach their own track, not stop short of it.
- A date window, if present, should sit centered in its aperture with no white sliver at one edge.
Dial printing is one of the hardest things for a replica maker to copy at full size. Look at the dial from an angle in daylight, not under a phone flash, and compare the spacing of the subdials against a photo of the real reference.
Check 3: The Movement and Case Back
A see-through case back makes this check direct. Genuine Portugieser Chronograph models use an IWC automatic chronograph movement with proper finishing on the bridges, and the rotor is decorated rather than stamped. Counterfeits often hide a generic chronograph module, or glue an engraved plate over an unrelated movement. Compare the reference and serial numbers engraved on the case back rim against the paperwork, and confirm the engraving is cut into the metal rather than printed on the surface.
Check 4: Serial Number, Papers, and Packaging
- Serial and reference numbers on the case back should match the warranty card and certificate.
- Booklets should show consistent typography and a model-specific reference, not a generic chronograph label.
- Box hardware, lining, and print quality should match the era of the watch.
- Service records or a purchase receipt from an authorized dealer add weight to any claim of authenticity.
Check 5: Price and Seller Behavior
A genuine steel IW371633 sells on the used market well above what a counterfeit costs to produce. If a private seller quotes a price far under the going rate, offers no service history, refuses to meet at a watchmaker for inspection, or pushes for a fast wire transfer, the risk is high. Ask for a timestamped photo of the case back with today's date, and use a payment method with buyer protection when you cannot inspect the watch in person.
How Replica Grades Change the Answer
Not every fake is a cheap knockoff. High-grade replica watches copy case proportions, dial printing, and even the movement layout closely enough that a photo comparison alone will not settle the question. That is why the checks above focus on details a photo cannot fake well: engraving depth, lug finishing, crystal edge, and paperwork that matches the serial number. On a well-made replica the tell usually shows up in movement decoration, the feel of the winding action, and the font used on the case back.
When to Get a Professional Opinion
An independent watchmaker can open the case back, time the movement on a machine, and confirm the serial number against service records. A short inspection costs a fraction of what you would lose by paying genuine prices for a counterfeit. If you are the seller, the same inspection gives you documentation you can show a buyer, which often makes the sale faster and easier.
Quick Pre-Purchase Checklist
- Confirm the exact IW371633 specification from an official source.
- Compare case size, lug finishing, and crystal edge in person or in high-resolution photos.
- Check dial printing, subdial alignment, and hand lengths.
- Verify serial and reference numbers against papers and the case back engraving.
- Price the watch against current used-market listings before agreeing to anything.