Short answer
A fake IW371634 is a counterfeit copy of an IWC Portugieser Chronograph. Copies sell for about $40 to $600. The genuine watch uses a steel or gold case, a sapphire crystal, and an IWC calibre 79350 or 69355. No counterfeit uses those movements. Reference IW371634 sits in the 3716 block of Portugieser Chronograph numbers. Dealer listings disagree on the case metal and dial color for that number, so confirm the build with IWC before you pay.
What the reference covers
The Portugieser Chronograph has two generations. The 40.9 mm version ran from 1998 to 2020 with calibre 79350, a Valjoux 7750 base with a reworked gear train. The 41 mm version arrived in 2020 with calibre 69355. Both place the chronograph minutes at 12 and the running seconds at 6. Lug width is 20 mm.
IWC reference pages are the only reliable source for case metal, dial color, and case size on IW371634. Public spec pages copy each other and disagree.
How to check a watch in hand
Case
Measure across the bezel, crown excluded. A steel original measures 40.9 mm or 41.0 mm. Low-tier copies drift by 1 mm to 2 mm. The crown should screw down and sit flush with the case band. Plated brass shows a dull yellow tone at worn edges.
Dial and hands
- Applied numerals on the original have sharp edges and even polish. Copies show rounded edges and thin plating.
- Dial print on the original is thin and even. Copy print shows thick strokes and uneven spacing.
- Hands are leaf shaped and reach the minute track. Copy hands run short.
- Start the chronograph, run it 60 seconds, then reset. The hands must snap back to zero with no lag.
Movement
Ask for a photo of the movement and a video of the chronograph running. Calibre 79350 beats at 28,800 vibrations per hour, which is 8 beats per second. A quartz fake ticks once per second. A Chinese 7750 copy beats at the same rate as the original, so sound alone will not separate the two. Look at the rotor engraving and the balance assembly layout.
Weight
Put the watch on a kitchen scale. A steel case with a leather strap in this size lands near 80 g. A reading near 55 g means the case is not steel.
Price ranges
Fake listings cluster in three bands. Quartz copies run $40 to $90. Automatic copies with a Chinese 7750 run $150 to $300. Copies sold as Swiss made run $300 to $600. A genuine steel Portugieser Chronograph trades on the secondary market from about $5,000 to $8,000. A working IWC chronograph under $1,000 is the strongest single signal of a fake.
Legal position in the US
Importing a counterfeit watch is prohibited under 19 U.S.C. § 1526. U.S. Customs and Border Protection can seize the parcel and destroy it. The buyer can face a civil penalty. Selling a counterfeit is trademark infringement. A personal-use purchase is not a federal crime, but the goods stay subject to seizure.
Checklist before you pay
- Ask for a photo of the caseback engraving, including the reference and serial.
- Ask for a movement photo. A closed caseback with no photo is a stop sign.
- Ask for a video that shows the chronograph start, run, and reset.
- Compare the dial against the IWC page for that reference.
- Request a service quote from an IWC authorized service center. The quote confirms authenticity and settles the question.