Short answer

An IW323761 stays unverified until four things line up: the case engravings, the dial and case finishing under magnification, the movement inside the case, and the paperwork behind the sale. Most fakes fail at least two of those checks, and the movement is the check that gives them away. Work through the steps below in order before money changes hands.

Prerequisites

  • A 10x jeweler's loupe
  • Digital calipers that read to 0.01 mm
  • A gram scale accurate to 0.1 g
  • A timegrapher, or a phone timing app for a rough reading
  • Reference photos of a documented genuine IW323761 from an auction archive or a dealer listing
  • A caseback opening tool, or a watchmaker who will open the case for you

How to check an IW323761, step by step

  1. Photograph the watch as offered, including the caseback and any papers, so you hold a record of what the seller claims.
  2. Measure the case with calipers and write down the diameter, the thickness, and the lug width.
  3. Compare those numbers with the published spec for the reference. A gap of 0.5 mm points to a copied case.
  4. Weigh the watch head on the gram scale, then weigh it again with the bracelet or strap fitted.
  5. Set both weights against a documented genuine example of the same configuration.
  6. Read the reference engraving on the caseback under the loupe. The characters should be sharp, spaced at equal intervals, and cut to the same depth.
  7. Check the serial engraving the same way, then record both numbers.
  8. Study the dial text at 10x. Compare letter spacing in the brand name, stroke thickness, and the position of the text block against the markers.
  9. Inspect the hour markers and hands. Lume fill should sit level with the metal frame and match in color from marker to marker.
  10. Turn the watch under a strong light and look at the crystal. Genuine IWC sapphire carries an anti-reflective treatment that kills most glare. A fake shows a heavy blue or purple cast.
  11. Examine the crown engraving and thread the crown in and out. The marking must be centered and deep, and the threads should resist in a steady way.
  12. Open the caseback and read the caliber number on the movement.
  13. Match that caliber against the caliber IWC used for this reference. Fakes hide a stock third-party movement under a decorated rotor with a copied brand marking.
  14. Check the movement finishing at 10x: Geneva stripes on the bridges, circular graining, blued screws, and clean jewel settings.
  15. Run the watch on a timegrapher in the dial-up and crown-down positions and record rate, amplitude, and beat error.
  16. Send the reference number and serial to an IWC service center or authorized dealer and ask them to confirm the pair against production records.
  17. Ask the seller for the original invoice, warranty card, and service history, then call the dealer named on those papers.
  18. Have a watchmaker who handles IWC watches open the case and give you a written opinion.

Red flags that settle it fast

  • The asking price sits far under the current market for the reference.
  • The seller refuses to open the caseback or to let a watchmaker do it.
  • The reference and serial never appear together on a service record.
  • Font weight shifts between the brand name and the model line on the dial.
  • End links flex or rattle against the case.
  • The box, papers, and warranty card carry reference numbers that do not match the watch.

If the watch turns out to be fake

Keep the listing, the messages, and the payment records. File a dispute with the payment platform, report the listing to the site that hosted it, and report the sale through the US government counterfeit reporting portal. If the watch was sold to you as a replica, no report applies, but the same checks still tell you whether the build quality matches the price you paid.