Most fake IW371475s give themselves away in three places: the subdial printing, the date window, and whatever you see through the caseback. Put a loupe on those and you usually have an answer inside a minute. Everything else on the watch is just confirmation.
What the IW371475 is meant to be
The reference sits in IWC's Portugieser Chronograph 3714 generation. That means a steel case around 40.9mm across, roughly 12.3mm thick, a slim bezel, a dial with two subdials stacked vertically at 12 and 6, a date at 3, and a display back. Inside is calibre 79350, which is a Valjoux 7750 base that IWC stripped down and reworked into a two-register chronograph. The pushers are pump style, the crown is signed, and water resistance is rated at 3 bar.
One caveat before you start comparing. IWC shuffles dial colors, index styles, and strap combos across individual reference numbers, and some variants were sold through limited distribution. Pull the exact specs for your reference from IWC directly rather than trusting what a seller tells you. If a listing claims a dial color that IWC never published for that number, stop there.
The dial is where cheap copies live
Printing quality is the fastest tell. Genuine Portugieser dials use crisp, slightly raised print with no bleed into the surrounding lacquer. Fakes tend to look flat and a touch gray, especially the minute track. Run a fingernail across the track on a real one and you feel a subtle step. On a copy it is usually smooth.
- Subdial spacing. The two registers should sit on a clean vertical axis, evenly sized, with the small seconds at 6 and the chrono minutes at 12. Copies often shift one subdial a fraction off center or size them unevenly.
- Subdial rings. Genuine rings are thin and sharply defined. Replicas often show a thicker ring with softer edges.
- Hands. Leaf-shaped, faceted, and properly finished on the edges. Look for tool marks or a brushed-looking bevel on the underside.
- The logo. The applied IWC lettering should sit level, with consistent stroke weight and no glue haze around the feet.
- Date window. The cut should be sharp-cornered and the wheel font matches the rest of the dial. This is a very common miss. Fakes often use a generic date disc with a slightly different numeral shape.
Case, crown, and pushers
The case should feel dense in the hand for its size, with lugs that taper cleanly and a polished flank that transitions into a brushed surface without a mushy line. Check the crown engraving under magnification. The Probus Scafusia mark should be deep and legible, not a shallow stamp. Push the chrono pushers: the start should have a firm, positive click and the reset should snap back hard. A spongy or grinding pusher on a Valjoux-based movement is a bad sign, either a fake or a badly serviced watch.
The caseback and movement
Sapphire display back, held by a screw ring or a set of small screws depending on the generation. Engraving depth matters. Genuine reference numbers and serials are cut cleanly, evenly spaced, and sit on a properly finished surface. Copies tend to laser-etch shallow text with slightly rounded characters.
Then look at the movement. A 79350 shows a column of polished components, blued screws, and perlage or Geneva stripes on the bridges depending on the year. A cheap fake will show a stock 7750 with minimal decoration, or worse, a Chinese chrono module with a rotor that does not match. If the seller will not show you a clear macro of the movement, that alone tells you something.
Strap and hardware
Genuine alligator straps have visible scale structure that varies across the strap, with hand-stitched edges and a signed tang or deployant. Most replicas use embossed calf with a uniform pattern that repeats. Flip the strap and look at the lining and the spring bars. Cheap spring bars with no marking are common on copies.
What the better replicas actually get right
Honest answer: the top tier of Portugieser copies now nail the case proportions, the dial layout, and the sapphire, and at arm's length they pass. They still lose on printing crispness under a loupe, on the date wheel font, on movement decoration, and on strap leather. If you are buying a replica knowingly, judge it on those four things and skip the rest. If you are buying what you believe is a genuine watch, those four things are exactly where to push hardest.
Quick checklist
- Loupe the minute track and subdial rings for print quality.
- Compare the date numeral font to a known genuine photo of the same reference.
- Check crown engraving depth and pusher feel.
- Read the caseback engraving for depth and character shape.
- Inspect the movement for blued screws and proper bridge finishing.
- Verify the dial color and index style existed for that exact reference.