Short answer
Replica IW371663 means a copy of an IWC Portugieser Chronograph. The genuine watch is a 41 mm stainless steel chronograph with an automatic movement and a two-register dial. Copies sell for about $150 to $600. IWC does not make them and does not authorize them.
Reference IW371663 does not appear in the public catalogs I checked. IW3716 is a large reference family, and dial colors, strap types and market codes vary inside it. Ask the seller for the exact dial color and a caliper photo of the case before you pay.
Specs of the genuine watch
- Case: stainless steel, 41 mm diameter
- Movement: IWC calibre 69355, automatic chronograph, 4 Hz
- Power reserve: about 46 hours
- Crystal: sapphire front and back
- Water resistance: 30 m
- Dial: small seconds at 6 o'clock, chronograph minutes at 12 o'clock
- Hands: leaf shape, applied numerals, railroad minute track
- Strap: leather
Earlier Portugieser Chronographs used reference IW3714. The IW3716 watches sit alongside them in the current line.
How the copies are built
Cases on the better copies match the 41 mm figure within a fraction of a millimeter and use 316L steel. Crystals are sapphire on the top grade and mineral glass on cheap ones.
The movement is the hard part. A stock Valjoux 7750 has subdials at 12, 6 and 9 o'clock. The IW3716 dial has two subdials, at 12 and 6. Makers solve this in three ways: a reworked 7750 with one hand removed or hidden, a clone movement built to the two-register layout, or a quartz module. Ask which one is in the watch.
Checks before you buy
- Case diameter, measured with calipers in a photo.
- Movement photo through the display back. Check rotor engraving and bridge finish.
- Subdial positions and hand lengths.
- Date window, if the dial has one, and the font of the numerals.
- Timegrapher reading, if the seller has one.
- Crown position and stem length.
Legal note for US buyers
Title 18, Section 2320 of the US Code makes trafficking in counterfeit goods a federal crime. US Customs and Border Protection can seize counterfeit shipments at the border. IWC Schaffhausen holds the trademark for the IWC name. A replica is not a genuine IWC watch, and IWC will not service it.