A replica IW371743 and the genuine IWC Portugieser Chronograph differ in four places you can measure: case thickness, movement, dial print, and caseback engraving. The outside can look close. The inside cannot. Check each point with tools, not with seller photos.
Reference facts
IW371743 is a steel Portugieser Chronograph with a silver-plated dial, gold-plated hands and indices, two subdials at 12 and 6, and no date window. IWC lists the case at 40.9 mm across. The movement is caliber 79350.
Case and thickness
The genuine case measures about 12.3 mm thick. Replica cases built around an Asian 7750 run thick, most in the 13.5 mm to 14.5 mm range. Calipers settle this in ten seconds. Lug width is 20 mm. Look at the lug curve against the strap: a replica lug sits square where the genuine lug tapers.
Movement
Caliber 79350 beats at 28,800 vph, 31 jewels, 44 hours of power reserve, built on Valjoux 7750 architecture. The copy uses an Asian 7750. Beat rate matches. Finishing does not. Geneva stripes, rotor engraving depth, screw heads, and balance cock shape all show the gap. Ask for a photo of the movement through the caseback before payment.
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Dial and hands
Genuine dial: silver plating, applied indices, leaf hands with a polished bevel, minute track with crisp edges. Replica faults show at 2x magnification. Thick subdial rings. Uneven lume plots. Flat hands with no bevel. A logo that sits a hair high or low. Subdial hands rest at zero after a chrono reset. A drifting minute counter means the reset hammer is off.
Caseback, crown, pushers
The genuine caseback carries an engraved reference and serial plus a sapphire window. Replica engraving is shallow and the font weight is wrong. Pushers on the copy feel soft and can stick. Wind the crown 20 turns and listen for a dry rotor scrape.
Checks before purchase
- Measure thickness with calipers.
- Photograph the movement through the caseback.
- Reset the chrono and confirm both subdial hands return to zero.
- Time the watch over 24 hours. Past 15 seconds a day, budget for service.
- Compare the serial and reference engraving against IWC records.
Cost and risk
Genuine secondary prices for IW371743 sit in the four figures USD. Verify against a current dealer listing before you compare. Replica prices run from about 300 to 700 USD. US Customs can seize counterfeit goods and the shipment is lost with no refund. Import rules vary by country, so confirm the local statute first.
What is unknown
Replica batches change without notice. Case thickness, dial shade, and movement finish vary between factories and between runs from the same factory. Photos from one batch do not describe the next. Treat every spec here as a check to run, not a guarantee.