The IW371497 belongs to the IWC Portuguese Chronograph family. A replica of it stands or falls on four numbers: case width, case thickness, subdial position, and hand length. Ask for caliper photos before you pay. Most listings give none.
What the reference is
IWC lists the base Portuguese Chronograph as a steel watch with a 40.9 mm case, 12.3 mm thickness, and 30 m water resistance. The movement is caliber 79350: automatic, 28,800 vph, 44-hour power reserve, built on an ETA 7750 base. The dial carries two subdials, a 30-minute counter at 12 and small seconds at 6. There is no date window. The numerals are applied, the hands are leaf-shaped, and the caseback has a sapphire window.
The suffix 97 marks a dial and strap variant inside the 3714 family. IWC does not publish a separate spec sheet for each suffix, so confirm the dial color with the seller from a photo, not from the listing text.
Check 1: thickness
The genuine case measures 12.3 mm across the caseback. Replicas running an Asian 7750 with a modified seconds module land between 13.5 mm and 14.5 mm. That 1 to 2 mm shows at a shirt cuff and against the wrist. Request a caliper photo with the jaws on the caseband, not on the crystal.
Check 2: subdial spacing and numerals
On the genuine dial the subdials cut into the 12 and the 6. The overlap is deliberate. Low-grade replicas shrink the subdials and float them clear of the numerals, or print the numerals flat instead of applying them. Ask for a macro photo at 12 o'clock. Look at the numeral edge. An applied numeral casts a shadow line.
Check 3: the running seconds
The 7750 puts running seconds at 9 o'clock. IWC moved it to 6. Replica makers copy this with a module, and the module is the part that fails first. A photo of the movement with the caseback open settles it. The 79350 rotor carries an engraved IWC medallion. Plain rotors and unmarked bridges are a different movement.
Claims to discount
- "Swiss ETA 7750." Most stock is an Asian 7750 or a Chinese clone. Ask for the rotor photo.
- "1:1." This means nothing without measurements. Ask for numbers.
- "Water resistant 30 m." Replica gaskets are not pressure-tested. Do not swim in it.
- "Same weight as original." Case weight varies with the movement and the caseback steel. It is not a reliable test.
Questions for the seller
- Caliper photo of case width and thickness.
- Movement photo, rotor side, caseback off.
- Macro photo of the dial at 12.
- Photo of the caseback engraving between the lugs.
- Return terms in writing, with a deadline.
A replica is not the original watch and will not hold value. Buy on the measurements and the return policy, not on the photos of the box.