Quick answer
A fake IW371497 fails in four places: case size, subdial function, movement, and caseback engraving. Measure the case first. The Portugieser Chronograph in the 3714 family measures 40.9 mm across. The current 3716 family measures 41 mm. Low-grade copies run 42 mm to 43 mm so a stock movement fits. High-grade copies match the number, so size alone does not settle it. Then stop the chronograph and watch the subdial at 6 o'clock for 60 seconds.
Confirm the reference first
IWC reference numbers carry a family code and a dial and strap code. IW371497 sits in the 3714 or 3716 range. IWC's public reference list is the source for the exact dial color, case metal, and strap for that number. Buyers who compare a watch against photos of the wrong reference will find faults that are not faults. Get the number, then get photos.
Case and dimensions
- Diameter: 40.9 mm on the 3714 family, 41 mm on the 3716 family.
- Height: about 12.3 mm on the 3714 family.
- Lug width: 20 mm.
- Water resistance: 3 bar.
- Finish: high polish on the case and bezel.
Calipers cost less than a service. Measure the head with the strap off. A 1 mm gap is visible in a side photo and easy to miss in a wrist shot.
Dial and hands
The dial has two subdials. The chronograph minute counter sits at 12. The running seconds sit at 6. The date window sits at 3. Numerals are applied, not printed, and they sit above the dial surface. Hands are feuille leaf shape. Print quality under a 10x loupe separates grades. Copies show soft edges on the logo, uneven spacing between letters, and a date font that differs from the genuine one. The date wheel on a copy often sits off center in the window.
Movement
Older 3714 references use calibre 79350, a modified Valjoux 7750 with 44 hours of power reserve at 28,800 vph. Current references use calibre 69355, an in-house column wheel design with 46 hours of power reserve. A stock 7750 keeps a 12-hour counter at 6 o'clock and a running seconds hand at 9 o'clock. IWC moved the running seconds to 6 and dropped the third subdial. That difference is the single most useful test. If the subdial at 6 sits still while the watch runs and the chronograph is stopped, the watch is not an IWC 79350.
Caseback, serial, and paperwork
The caseback carries the reference and a serial. The same serial appears on the movement. Ask IWC or an authorized service center to confirm the serial against their records. Copies reuse one serial across many units, so a search for that number returns the same watch from several sellers. Ask for the guarantee card, the box, and any service paperwork. A seller who cannot supply a serial photo with the date is a seller to skip.
Checks in order
- Read the reference and serial from the caseback photo.
- Verify the serial with IWC.
- Measure diameter and height with calipers.
- Stop the chronograph. Watch the 6 o'clock subdial for 60 seconds.
- Compare dial print, numeral fit, and date font under a loupe.
- Check engraving depth and letter shape on the caseback.
- Weigh the watch head and compare with a known example.
Limits of photos
Photos hide case thickness, bracelet flex, and rotor noise. A video call with the watch running covers the subdial test. For anything above a low price, a service center inspection is the final step. IW371497 production details change by year, so confirm the calibre for the specific reference before you judge a watch.