Short answer
A fake IW371431 is a counterfeit of the IWC Portugieser Chronograph. The real watch has a 40.9 mm steel case, measures 12.3 mm thick, and holds IWC calibre 79350. Copies miss on three points: thickness, subdial layout, and movement finish. Measure the case, count the subdials, and inspect the movement before you pay.
What IW371431 is
IW371431 sits in the IWC Portugieser Chronograph line. IWC built the 3714 base number across dial, strap, and edition versions, so one base number covers several reference codes. IWC's reference list is the source for the dial color and strap on IW371431. I did not find a spec sheet published for this reference on its own.
The layout is a two-register chronograph. The 30-minute counter sits at 12 o'clock. The running seconds sit at 6 o'clock. A watch with three subdials is not this reference.
Dial and hands
- Hands are leaf shaped and thin. The Portugieser Chronograph dial carries no luminous material. If the markers or hands glow in the dark, the watch is not this reference.
- Applied numerals sit on the dial with polished edges. Copies show glue at the base and uneven height.
- The IWC and SCHAFFHAUSEN print uses thin strokes. Copies print heavy and fill the gaps inside letters.
- The date aperture sits at 3 o'clock. Check the window edge. A rough cut or a white plastic ring shows on copies.
- Subdial spacing comes from the movement. A copy built on a stock 7750 puts the small seconds at 9 o'clock instead of 6.
Case and caseback
Genuine numbers: 40.9 mm across the bezel, 12.3 mm thick. Counterfeit listings report case widths of 41.5 mm and up, with depths of 13.5 mm to 15 mm. Use calipers. A photo hides 2 mm.
IWC rates the Portugieser Chronograph at 3 bar. A caseback stamped 100 m or 10 ATM does not match the reference data. The 3714 uses a sapphire display window, so you can see the movement without opening the case.
The reference number sits between the lugs. The case serial sits on the caseback. Laser engraving on copies is shallow, gray, and uneven at the edges. Factory engraving cuts clean and shows a bright edge under light.
Movement
Calibre 79350 is a Valjoux 7750 base. IWC modifies the gear train to move the running seconds to 6 o'clock. Specs: 25 jewels, 28,800 vph (4 Hz), about 44 hours of reserve, 30-minute chronograph counter. IWC finishes the rotor and bridges with Geneva stripes and perlage.
Copies use an Asian 7750, a Sea-Gull movement, or a quartz module behind a decorative plate. Run the chronograph. A 7750-based watch starts with a firm click and the chronograph hand steps 8 times per second. A quartz copy ticks once per second. A hand-wound copy has no rotor weight when you turn the watch.
Price and paperwork
US retail for a steel Portugieser Chronograph on a leather strap runs about $8,000 to $8,600. Used examples trade between $5,000 and $7,500. A full set has a warranty card with the reference and case serial, a booklet, and a box.
Any listing at $300 to $900 is a counterfeit. Prices move, so check current listings before you judge a deal.
Verification steps
- Get the reference number and the case serial from the seller.
- Send both numbers to an IWC boutique or an authorized service center.
- Ask for photos of the movement, the crown, and the engraving between the lugs.
- Measure diameter and thickness with calipers.
- Ask for IWC service receipts. Those carry the case number.