There is no IWC reference number IW938604. IWC's modern references use the letters IW followed by six digits, and the 9386xx range does not appear in the brand's catalog, new or vintage. So when someone searches for a "fake IW938604," they are almost always looking at a number that came from a seller, a marketplace listing, or a caseback stamp, not from Schaffhausen.
What it usually turns out to be: a dealer's internal SKU, a listing ID on a replica site, a misread or mistyped reference, or a number stamped onto a caseback to make a replica look documented. None of those make it an IWC model.
How IWC reference numbers actually work
IWC has used a consistent format for decades. The letters IW sit in front of a six-digit number, and the first four digits point to a model family. Portugieser chronographs sit around IW3716xx, Pilot's watches around IW3777xx and IW3270xx, Portofino around IW3565xx, Aquatimer around IW3767xx and IW3290xx, and the big Portugieser automatics around IW5007xx. When I see a reference, the first thing I do is match that prefix to a family I recognize.
IW938604 fails that check. There is no 9386 family. The number also has eight digits after the letters, which is one more than IWC uses on its own references.
Where the number probably comes from
- Replica seller SKU. Many replica storefronts assign their own codes so buyers can find the same watch again. Those codes often mimic IWC formatting to look official.
- Marketplace listing IDs. Auction and classified platforms generate internal item numbers that have nothing to do with the maker.
- Caseback engraving. Cheap replicas sometimes stamp a random string on the back because a blank caseback looks suspicious to a first-time buyer.
- A typo or a misread. Digits like 3, 8, and 6 blur together on engraved casebacks and in low-resolution listing photos.
How to check whether the watch is genuine
Start with the reference itself. Look it up against IWC's own catalog and a reference database that groups models by family. If the number does not resolve to a real model with a real case size, dial layout, and movement, stop there.
Then check the caseback. A genuine IWC carries the reference number and a separate serial number, and those two are different strings. A single eight-digit number stamped alone, with shallow or uneven lettering, is a warning sign. I also compare the movement to the reference, since each IWC reference is tied to a specific caliber, and a mismatch between the caseback and the movement is one of the easiest tells to confirm.
Finally, weigh the paperwork. Box, booklet, and card should all carry the same reference and serial. When a seller insists the number is IW938604 and brushes off questions about the caliber, the model family, or the year of production, that is your answer.
The short version
IW938604 is not an IWC reference. Treat any watch described that way as a replica or a listing error until someone can point to the model in IWC's official catalog.