Short Answer

IW93857 is a reference string that appears in online watch listings, marketplace posts, and social media ads. The IW prefix belongs to IWC Schaffhausen, whose published references follow the IW plus five digits pattern. If the full string does not match a model in the brand's own catalogue, the listing is not describing a production watch. That does not automatically prove a fake, but it moves the item into the category of things you verify before you send money.

A reference number is only a label. Counterfeit sellers reuse real references, invent new ones, and mix prefixes from different brands. Your job is to test the physical watch against the claim, not the claim against itself.

Before You Start

  • Ask the seller for the full reference, serial, and case diameter in writing.
  • Request original photos with a dated object in frame, such as a coin or card.
  • Have a local watchmaker available for an in-person inspection.

Step-by-Step Verification

  1. Look up the exact reference string in the manufacturer's published catalogue or an authorized dealer's system. If nothing matches, stop here and treat the listing as unverified.
  2. Request the serial number and reference number engraved on the case back, then compare both against the paperwork.
  3. Compare the engraving on the case back between the lugs. Genuine engraving is crisp, evenly spaced, and cut into the metal rather than printed on top of it.
  4. Examine the dial printing with a loupe. Check letter spacing, font weight, and the alignment of the indices against the minute track.
  5. Inspect the movement through a display back, or ask a watchmaker to open the case. Look for finishing, jewel settings, and rotor engraving that match the brand's standard.
  6. Check the crown action and the date change. A gritty crown or a date that flips at the wrong hour points to a low-grade movement.
  7. Place the watch on a timegrapher and read the rate, amplitude, and beat error. A genuine mechanical movement holds a stable rate across positions.
  8. Compare the asking price against current resale listings for the same reference in the same condition.

Red Flags in IW-Prefixed Listings

  • The price sits far below the resale market with no stated reason.
  • The seller refuses an in-person inspection or a third-party authentication.
  • The photos are stock images or show a different watch than the one described.
  • The listing combines an IW reference with Rolex or Omega branding.
  • Payment is limited to wire transfer, gift cards, or crypto with no refund path.
  • The box, warranty card, and serial numbers do not agree with each other.

What to Do Next

Walk away from any listing that fails two or more checks. If you already own the watch and want a firm answer, take it to an authorized dealer or an independent watchmaker who services that brand. A hands-on inspection of the movement settles the question in minutes. Online photo opinions do not.