Short answer

A fake IW371752 shows on the caseback first. IWC cuts the reference number, the movement serial, and the case metal into the back with a laser. The cut is thin and even. Most copies use a shallow stamp or a printed label that sits on top of the steel. Check the caseback, then the movement, then the dial and hands, then the papers.

What IW371752 is

IWC writes references as IW plus six digits. IW371752 belongs to the Portugieser chronograph line. The layout has two subdials on a vertical line at 12 and 6 o'clock, a date window at 3, and leaf hands. Case size for this family runs 40.9 mm to 41 mm. Steel case, sapphire front glass, display caseback. Two movements have been used across the line: the 79350, built on a Valjoux 7750 base, and the in-house 69355. Confirm the reference on IWC's own listing for the year of the watch, since specs change between production runs.

Caseback and engraving

  • Text is cut into the metal, not printed. Drag a fingernail across the numbers. Real engraving has depth and a clean edge.
  • Lines on a real caseback: International Watch Co., Schaffhausen, the reference, the serial, the material, and a water resistance rating.
  • Serial is 7 or 8 digits. It matches the number on the movement bridge and on the warranty card.
  • Font weight is thin and spacing is even. Copies crowd the letters or use a bold font.
  • The sapphire window sits flush with the caseback rim. Copies show a lip.

Movement

Portugieser chronographs use a display caseback, so the movement is visible. Check these points.

  • Rotor decoration. A 7750 base can be plated and striped, but stripes on a real IWC run straight and stop at the screws.
  • Column wheel or cam. The 69355 uses a column wheel. The 79350 uses a cam and lever. Photos of both are published for comparison.
  • Chronograph feel. Pushers on a real watch start, stop, and reset with a short travel. Copies grind.
  • The IWC mark and the movement serial are engraved on the bridge. Print or paint means a copy.

Dial, hands, and printing

  • Numerals are applied, with a polished edge. Tilt the dial under a lamp. Painted numerals sit flat and show a border.
  • Text is crisp. IWC, SCHAFFHAUSEN, and AUTOMATIC hold even spacing.
  • Leaf hands have a center ridge and a beveled edge. Copies use flat stamped hands.
  • Subdial rings are printed thin. The date sits centered in the window.

Case, crown, and pushers

Measure the case with calipers. A reading of 40.9 mm or 41.0 mm across the case, without the crown, matches the reference. Lug width is 20 mm. The crown winds with light resistance and no wobble. Pushers return under spring tension. Copies show play in the crown tube and a loose reset.

Papers, box, and price

A full set has the IWC box, the manual, and a warranty card that lists the reference and the serial. Those numbers must match the caseback and the movement. IWC keeps a service record by serial, so a boutique or an authorized dealer can confirm the watch. Retail for a steel Portugieser chronograph sits in the high four figures to low five figures USD. Listings far under market are the main risk.

What to check before you buy

  1. Caseback engraving depth and font.
  2. Serial match across caseback, movement, and card.
  3. Movement photos against published reference photos.
  4. Case measurement with calipers.
  5. Pusher action and reset.
  6. Price against current market listings.

If a seller will not send photos of the caseback and the movement, stop. Those two photos answer most questions about a fake IW371752.