Quick answer
A replica IW371771 is a non-genuine copy of IWC's Portugieser Chronograph in that reference. Quality ranges from a low-cost quartz piece with a printed dial to a mechanical build with a working chronograph and a sapphire crystal. The movement and the dial finishing decide which one you have. Most people who research this reference are trying to authenticate a watch they own or are being offered, not to buy a copy.
What the reference covers
The IW3717xx range is the Portugieser Chronograph line. These watches share a design language: a round case roughly 40 to 41 mm across, a two-counter chronograph layout, applied numerals at 12 and 6, feuille hands, and a recessed subdial ring. Any copy of this reference has to reproduce that layout, and the layout is where most copies fail.
What separates a careful copy from a cheap one
- Movement. A column wheel chronograph based on the Seagull ST19 is the common mechanical base in mid-tier copies. Cheap copies use a quartz module or a stripped movement with a decorative chronograph.
- Dial print. Genuine dials use applied numerals and polished hands. Cheap copies use printed numerals with a flat finish.
- Case finish. Look at the transition between the brushed case band and the polished bezel. A sharp, even line takes real machining time.
- Crystal. Sapphire with an anti-reflective coating on both faces is standard on better copies; mineral glass with a blue tint is not.
How to evaluate a replica IW371771
Work through these in order. A failure at any step usually points to a lower tier build.
- Measure the case across the widest point with calipers and compare the number to the published reference specification.
- Photograph the dial straight on under diffuse light and check that both subdials sit on the same horizontal line.
- Run the chronograph and watch the sweep hand for stutter, which points to a quartz module.
- Listen to the movement with the case back against your ear and note whether the beat is smooth or grinding.
- Press the pushers and check for firm, short travel with a clean reset to zero.
- Time the watch over 24 hours against a reference clock and record the daily rate.
- Inspect the case back engraving under a loupe for shallow, uneven lettering.
- Compare the crown logo and the date font against published photographs of the genuine reference.
Legal and practical risk
Counterfeit watches carry real consequences in the United States. Goods bearing a copied trademark can be seized at import, and selling a replica as genuine is fraud. If you are buying a used IWC, treat the reference number as a starting point and verify the serial with the manufacturer or a qualified watchmaker.