The short answer
IW938105 does not match any reference number IWC Schaffhausen has ever published. Genuine IWC references follow a pattern like IW371617 or IW500705: the letters stay fixed, and the digits map to a model family, case material, dial, and strap. A six digit string starting with 938 sits outside every catalog block the brand uses. That tells you the code came from a seller, not a manufacturer.
So a search for "fake iw938105" is really a search for a listing. Someone saw that string on a replica storefront, a marketplace page, or a messaging app catalog and wanted to know what watch sits behind it. In most cases it is a generic automatic watch styled after an IWC Portugieser or Portofino, sold under an internal stock number that gets recycled once the batch runs out.
Why replica sellers use inventory codes
Replica operations rotate names. A fixed model name invites trademark takedowns, payment processor bans, and customs attention. A numeric SKU does not. It also lets the same seller move the same case between factories without updating the storefront. If you see IW938105 on one site and a different code on another for an identical photo, you are likely looking at the same wholesale catalog.
The codes also manufacture authority. Putting "IW" in front of a random number borrows IWC's two letter shorthand and makes a stock label read like a factory reference. Strip the letters and you have a plain inventory number with no horological meaning.
Checks that separate a replica from a real IWC
- Reference lookup: a genuine reference resolves in IWC's own model archive or a dealer's system. If it only appears on replica and resale pages, it is not real.
- Caseback engraving: real engravings are crisp, even in depth, and match the reference exactly. Replicas blur the text or mix fonts.
- Movement: IWC in house calibers are decorated and signed. Replica movements are generic and often stamped with a brand name that does not match the case.
- Price: a new IWC chronograph starts in the thousands of dollars. Anything in the low hundreds is not genuine, and no "factory overrun" story changes that.
- Papers and boxes: replica sets ship with cards that have no serial linkage to the watch.
The legal side in the United States
Buying a counterfeit for personal use is not the same as selling one, but the risk is not zero. CBP can seize counterfeit goods at the border, and trafficking carries real penalties under the Trademark Counterfeiting Act. Reselling is where people get into trouble. Even one online sale can draw a civil suit from the brand, and platforms hand over seller records when served.
If you are trying to identify a watch you already own
Take clear photos of the caseback, the crown, the dial text, and the movement if you can open the case. Measure the case with calipers. Then compare those numbers against the published specs for the model the watch claims to be. A 40mm Portugieser that measures 41.5mm with a 22mm lug width is telling you something. So is a date window that sits a half millimeter off center.
If the only identifier you have is IW938105, you are probably holding a replica or looking at one. There is no hidden factory reference to decode. Treat the number as a seller's internal label and move on.