Short answer
IW371613 is a reference for the IWC Portugieser Chronograph, a 41 mm steel watch with IWC's own 69355 movement. A fake IW371613 is a watch built to copy it and sold as a replica. Sellers of these watches use the words Swiss replica or super clone. The movement inside is Asian in almost every case: Seagull ST19, a decorated 7750 clone, or a quartz module behind a fake display back.
Price is the fastest filter. Real examples sit in the high four figures. Replicas sell from $60 to $700.
Checks that settle the question
1. Case back engraving
Real watches carry IW371613 and a serial number cut into the metal with sharp edges. Fakes carry laser-etched text with soft edges, wrong spacing, or the same serial number across many listings. The sapphire back on a real watch shows calibre 69355 with Geneva stripes, blued screws, and a signed rotor. Replica movements show a plain rotor, shallow engraving, and a balance wheel in the wrong place.
2. Case size
Measure across the bezel with calipers. The Portugieser Chronograph case measures about 41 mm. Replica cases run 1 to 2 mm wider or sit 1 to 2 mm thicker because the movement and spacer differ from the original.
3. Dial and hands
Real dials have dense, flat printing with clean edges on the logo and the Schaffhausen line. Subdial placement and any date window must match the reference page for IW371613. Fakes show thin print, misaligned subdials, and hands that sit flat instead of stepped.
4. Crown, pushers, crystal
The crown carries the maker's mark. Pushers on a real column-wheel chronograph start and stop with a firm click. Replicas feel soft or gritty and the reset snaps hard. The crystal is sapphire with anti-reflective coating on both faces, so the dial stays dark at an angle.
Before you pay
- Ask for a photo of the case back with the serial visible, plus a photo of the movement.
- Ask for the warranty card, box, and service papers. The numbers must match the case.
- Compare the asking price against completed sales for IW371613.
- Pay with a method that allows a chargeback if the watch fails inspection.
- Have a watchmaker open the case within the return window.
Legal position in the US
Trafficking in counterfeit goods is a federal crime under 18 U.S.C. 2320. Customs and Border Protection seizes counterfeit watches at import. A buyer who orders a replica can lose the shipment, and gets no warranty, no parts support, and no service from IWC. Selling a fake as genuine is fraud.
What is not public
IWC does not run a public serial number lookup for this reference. No online database confirms an IW371613 as genuine. Verification runs through the movement and the paperwork, or through a watchmaker who can open the case.