Short answer

IW371778 does not appear in IWC's published reference list that I could verify. Listings that use the string "IW371778" describe a copy of the IWC Portugieser Chronograph: a steel case near 41 mm, two subdials, a chronograph movement or a quartz substitute. Treat the reference as unverified. Check the parts against the real model.

What the genuine model looks like

The Portugieser Chronograph is one of IWC's core lines. Current refs sit near IW3716xx. The case measures about 41 mm across and 13.1 mm thick. Water resistance is 30 m. The movement is the in-house calibre 69355, a column wheel chronograph at 28,800 vibrations per hour with a 60 hour power reserve. Older refs such as IW3714xx used the calibre 79350, a modified Valjoux 7750 in a 40.9 mm case with about 44 hours of reserve. The dial has subdials at 12 and 6, small seconds at 9, sword hands, and applied numerals.

Three replica build types

  • Quartz. Seiko VK64 mecaquartz inside. The subdial at 6 is often a 24 hour indicator, not a chronograph minute counter. The sweep hand ticks once per second.
  • Asian 7750. Runs at 28,800 vph with 40 or more hours of reserve. Case thickness often passes 15 mm. Rotor noise is audible.
  • Marketed clone. A 7750 with decorative plates and engraving designed to mimic the 69355. The column wheel mechanism is not present.

Parts to inspect

  • Crystal. Genuine watches use sapphire with anti-reflective coating on both faces. Many copies use mineral glass.
  • Subdial spacing. The distance between 12 and 6 changes when the base movement differs.
  • Date window. Position and font vary between refs.
  • Caseback. Engraving depth and text layout are hard to copy.
  • Weight. Steel copies often weigh less than the original.

Legal status in the United States

Counterfeit watches are illegal to import and to sell in the US. 19 U.S.C. Section 1526(e) bars import of goods bearing a counterfeit trademark. 18 U.S.C. Section 2320 covers trafficking in counterfeit goods and carries criminal penalties. CBP seizes shipments at the border and the buyer receives nothing. A seller of a counterfeit item can also face civil claims from the trademark owner. IWC holds the trademark on its name and logo.

Red flags in a listing

  1. A reference number that no catalog lists.
  2. The phrase "Swiss made" on a watch that ships from Asia.
  3. Stock photos instead of the actual unit.
  4. No return policy or no payment protection.
  5. Claims that a copy is "identical" to the original.

What is not known

No public source confirms IW371778 as an IWC reference. IWC does not publish serial data. Movement origin claims from sellers are not verifiable from the outside. Any claim of a genuine "IW371778 super clone" is marketing text, not a fact.