Answer first

No Portugieser in IWC's current catalog has a 39mm case. The Portugieser Automatic 40, ref. IW3583, measures 40.4mm across the case at 3 and 9 o'clock. The Portugieser Chronograph 41, ref. IW3716, measures 41.0mm. A listing that says "fake Portugieser 39mm" points to one of three things: a replica of the Automatic 40 with a rounded number in the title, a replica of the older Chronograph ref. IW3714 at 40.9mm, or a case built to a size that matches no IWC reference.

Why 39mm shows up in titles

  • Rounding. Sellers shorten 40.4mm to 40 or 39 in a title.
  • Measurement at the bezel. A caliper on the bezel edge reads 1mm to 1.5mm less than the case at its widest point.
  • Copied specs. Some listings reuse the size line from a page for another brand.
  • A smaller shell. A 39mm case often holds a 21,600 vph movement or a quartz module, not a copy of an IWC calibre.

Case and lug numbers to check

Measure with a caliper, not a ruler. Take the reading on the case flank, crown side and opposite side, and add nothing for the crown. The Automatic 40 is 12.4mm thick. Both references take a 20mm strap. A watch that reads 38.5mm to 39.5mm at the flank is a 40.4mm case measured at the bezel, or a case from a smaller line.

Movements used in replicas

Genuine Automatic 40: IWC calibre 82200, Pellaton winding, 60-hour reserve. Genuine Chronograph 41: IWC calibre 69355, 4Hz, 46-hour reserve. The Chronograph ref. IW3714, sold from 1998 to 2019, used calibre 79350, a Valjoux 7750 base with a 44-hour reserve. Replica builds fall into three groups:

  • Quartz. The subdial hands step once per second or sit parked. The case is thin.
  • 21,600 vph mechanical. Six beats per second on the running seconds. No IWC Portugieser calibre runs at this rate.
  • Asia 7750 clone. 28,800 vph, eight beats per second. Most chronograph replicas use this base. Ask for a video of the chrono start, stop, and reset.

Dial and hand details

  • Applied numerals. Genuine markers are cut with facets. Replicas often use flat stamped markers.
  • Print. "IWC" and "SCHAFFHAUSEN" sit above and below the center. Check letter spacing and the serifs.
  • Subdial rings. The snailed finish on the two subdials shows concentric lines under a loupe.
  • Hands. The Automatic 40 uses leaf hands, polished on top and matte on the sides.

Price bands

IWC lists current prices on its own site. Steel Portugieser models sit in the high four figures in USD. Replica listings run from under $120 for quartz to $350 to $700 for a decorated 7750 build. A price below $150 for a mechanical chronograph with two subdials points to a quartz module behind a closed caseback.

US law and import

18 U.S.C. § 2320 covers trafficking in counterfeit goods. A first offense carries up to 10 years, a repeat offense up to 20 years. 19 CFR Part 133 lets US Customs and Border Protection seize and forfeit counterfeit merchandise at the border. Personal use is not a defense at import. One watch can be seized, and the buyer can face a civil penalty.

Questions to send a seller

  1. Caliper photo at 3 and 9 o'clock, in millimeters, on the case flank.
  2. Video of 30 seconds of the running seconds hand, then a full chrono start, stop, and reset.
  3. Caseback photo with the reference number and the movement finish.
  4. Photo of the lug width with a tape at the spring bar.

Answers that avoid numbers, or a caseback that stays closed in every photo, tell you more than the listing text does.