Short answer

A watch offered as an IWC with the reference IW93879 is unverified until the case, dial, movement, and serial number all line up with IWC's own records. Reference strings get typed onto casebacks, copied between listings, and reused across batches of counterfeits, so the string itself proves nothing. Verify in the order below, from the cheapest check to the most conclusive one.

Prerequisites

  • A 10x jeweler's loupe
  • A phone with macro mode or a clip-on macro lens
  • Digital calipers
  • Any box, papers, warranty card, or invoice that came with the watch
  • Access to an IWC authorized service center and an independent watchmaker

How to verify a watch sold as IW93879

  1. Copy the full reference string from the caseback exactly as it is engraved, including the IW prefix, the digits, and any slash or hyphen.
  2. Photograph the caseback, dial, crown, and clasp in macro mode with even lighting and no flash glare.
  3. Measure the case diameter and lug width with calipers and compare those numbers to the specification for that IWC reference family.
  4. Examine the dial text under the loupe, checking the brand name, the model line, and any depth rating for font weight, spacing, and alignment.
  5. Compare the date window position, aperture shape, and date font against photos of a confirmed genuine example of the same family.
  6. Study the caseback engraving for cut depth, letter spacing, and sharpness of the edges, since stamped or laser-etched fakes show shallow, rounded characters.
  7. View the movement through the display back, or have a watchmaker open the case, and confirm the caliber marking, finish, and rotor engraving.
  8. Submit the reference and serial number to an IWC authorized service center or boutique and ask them to check it against their service records.
  9. Request the original invoice, warranty card, and service papers from the seller, then compare the serial on each document to the serial on the case.
  10. Pay an independent watchmaker for a written authentication opinion before you transfer money or list the watch for sale.

Red flags that point to a counterfeit

  • The reference string does not appear in any IWC catalog or service record
  • Case dimensions differ from the published specification by more than a fraction of a millimeter
  • Engraving looks etched rather than cut, with flat tops and soft edges
  • Papers and box arrive without a matching serial, or the serial is printed on a sticker
  • The seller refuses an in-person inspection or a watchmaker's opening of the case

If the watch fails verification

Stop the transaction, keep every photo and message, and ask for the serial number in writing. A failed check is not proof of intent, but it is grounds to walk away. If you already own the watch, a written authentication report from an independent watchmaker gives you something concrete to send to the seller, your payment provider, or a customs authority.