The short answer
The IW371655 sits in the IWC Portuguese Chronograph IW3716 family: a stainless steel case around 41 mm across, twin subdials, applied Arabic numerals, feuille hands, and a self-winding chronograph movement. A replica worth buying copies those proportions and that dial layout first. Movement brand and caseback engraving matter second. Before you send money, confirm the measured case diameter, the subdial positions, the lug and strap width, and the exact dial and strap combination for the reference you were quoted. If the seller cannot show caliper measurements and a clear macro of the dial print, stop there.
Prerequisites
- Reference photos of the genuine IW371655 from the manufacturer catalogue or an auction archive.
- Digital calipers or a millimeter ruler.
- A loupe or a phone with macro mode.
- A seller who answers questions in writing and accepts returns.
Step-by-step checks
- Confirm the reference number. Ask the seller to photograph the caseback and any papers. The IW3716 family spans several dial and strap combinations, so match the dial color, index style, and strap material to the exact reference quoted.
- Measure the case with calipers. The Portuguese Chronograph case reads close to 41 mm across, excluding the crown, and roughly 12 to 13 mm thick. Measurements outside 39 to 43 mm mean a different watch or a rescaled copy.
- Check the subdial layout. Running seconds sits at 6 o'clock and the chronograph minutes counter at 12. Compare the spacing between the two rings and the dial center. Replica dials often crowd the subdials inward or print the rings too thick.
- Read the dial print under magnification. Lettering should be sharp with even stroke weight and level baselines. Fuzzy edges, uneven letter spacing, or a crooked International Watch Co. line are disqualifiers.
- Inspect the hands and numerals. Feuille hands taper to a fine point. Applied numerals sit flat against the dial with clean edges. Check that both hands are level and clear the dial surface.
- Cycle the chronograph ten times. Pushers should click once per press and the hands should snap back to zero with no drift. A slow reset or a wandering seconds hand points to a cheap module.
- Wind and set the movement. Hand-wind 20 turns, set the time, and watch the sweep. A 4 Hz mechanical movement advances in small steps. A hard once-per-second tick means quartz inside a mechanical case.
- Study the caseback engraving. Reference number, serial, and caseback finish should be crisp and centered. Shallow, off-center, or misspelled engraving is the fastest reason to refuse.
- Measure the strap. Lug width on this case is 20 mm on most variants. The strap should sit flush with no gap at the lugs. Genuine alligator shows irregular scale patterns rather than a uniform print.
- Request a movement photo and a timegrapher reading. A rate between minus 10 and plus 15 seconds per day with healthy amplitude is a reasonable floor for a usable copy.
- Agree on terms before paying. Get the price, shipping method, return window, and payment type in writing. No-return listings and irreversible transfers are the two most common ways buyers lose money.
Red flags
- Photos reused from another dealer, with mismatched backgrounds or lighting.
- No caseback shot, no movement shot, and no measured dimensions.
- A price far below the going rate for the tier you requested.
- Pressure to pay by wire or gift transfer with no receipt.
Legal note
Counterfeit watches infringe registered trademarks and are illegal to import or sell in the United States and the European Union. Customs officers can seize a shipment and the buyer usually gets nothing back. Treat any replica purchase as an informed personal risk and keep every message, invoice, and payment record.