Short answer
A fake IW371673 is a watch sold as an IWC Portugieser Chronograph that IWC did not build. The reference number IW371673 does not appear in the IWC catalog pages checked for this guide. Confirm the number exists before you judge a watch. If IWC has no record of it, the watch on the table is a replica, a redial, or a mislabeled reference.
Check the reference number first
IWC reference numbers carry the letters IW in front of six digits. IW371673 fits that format, so the code looks correct on paper. The code alone proves nothing. IWC stamps the reference between the lugs at 12 o'clock and on the caseback. On a genuine watch the engraving is shallow, sharp, and even. On a copy the digits sit deep and wide with rounded edges.
Compare the number on the watch to the number on the box label, the warranty card, and the IWC digital certificate. Three of those four should match.
Case and dial tells
The 3716 block of Portugieser Chronograph references uses a 41 mm steel case about 13 mm thick. Copies run 1 mm to 2 mm thicker, which shows at the lugs.
- Subdials sit at 12 and 6 o'clock. A 7750-based copy keeps the running seconds at 9.
- Numerals are applied and polished. Copies glue on flat numerals that sit low.
- Genuine crystal is box-shaped sapphire with coating on both faces. Most copies coat one face, so the dial reads flat under light.
- Pushers on a genuine watch start and stop with a short, firm click. Copies feel soft or gritty.
Movement
IWC fits current Portugieser Chronograph 41 models with caliber 69355, a self-winding column-wheel chronograph. It runs at 4 Hz and holds about 46 hours of power reserve. The rotor is skeletonized and the bridges carry Geneva stripes and perlage.
Copies of this reference use a Chinese copy of the Valjoux 7750, a Seagull ST19 hand-wound chronograph, or a decorated automatic with a fake plate. A Swiss ETA 7750 inside a copy is possible. That is still not an IWC caliber, and IWC will not service it. Ask a watchmaker to open the caseback and read the calibre number on the bridge.
Price and paperwork
Steel Portugieser Chronograph models list near $8,000 from IWC. Secondhand dealer listings trade below that. An unworn IW371673 at $400 to $900 is a replica. Papers matter: IWC box, warranty card with the reference and serial, and service records if the watch is over five years old.
Replica grades and their tells
- "AAA" or "1:1" grade: 7750 copy, wrong thickness, printed caseback text.
- "Super clone": correct 41 mm case, but rotor engraving is etched, not stamped.
- "Swiss made" movement: an ETA 7750 in a copy case. Still not an IWC caliber 69355.
How to verify before you buy
- Find the reference on iwc.com. If it is not there, stop.
- Ask for photos of the caseback, the lugs, and the movement.
- Match the serial to the warranty card and digital certificate.
- Have a watchmaker read the caliber number inside.
- Pay after the movement is confirmed.
What is not confirmed here
IWC's product page for IW371673 was not found in the sources checked. Production years, dial colors, and the exact caliber for that reference are not confirmed in this guide. Ask IWC or an authorized dealer for the reference sheet before you spend money.