The short answer
"Fake IW93820" is a listing code, not a watch. Sellers borrow the IW prefix that IWC uses for its references, bolt it onto a five digit number, and end up with a string that looks official at a glance. IWC's own references run IW plus six digits, things like IW356501 or IW371446. No model in the recent catalog carries 93820. Read the whole thing as a seller's internal SKU for a counterfeit dress watch in the Portofino mold: slim stainless case, plain dial, leather strap.
Where the code comes from
The number does not come from IWC. It comes from the workshop that built the watch, or from the reseller who bought a batch and needed a name for it. These codes circulate on wholesale sheets long before anything reaches a retail listing, and they stay stable while the watch underneath them changes. Order IW93820 in March and you may get one movement. Order it in September and you may get another. Same code, different watch.
How to check whether a reference is real
Three checks, in order. Search the number on IWC's own site. Count the digits after IW. Then look at how the seller writes it, because variation is a tell: iw93820, IW 93820, IW-93820. A real reference does not drift from listing to listing.
If you have the watch in hand, the caseback is where fakes give themselves up. Genuine references are engraved with consistent depth and spacing, and the serial matches the paperwork and the movement. Replica engravings are shallow, or the same serial repeats across units. Open the back and the movement settles it: an unfinished rotor, no decoration, a Chinese or Japanese workhorse sitting where a Swiss calibre should be.
What the listing does not tell you
Movement first. The same code ships with Miyota, Seagull, or a rough ETA clone, and the seller often does not know which until the batch lands. Water resistance is the second fiction. "50m" on a replica means splash resistant at best, and sometimes not even that, because the gaskets are an afterthought. Third, finishing: plating thickness, crystal material, anti-reflective coating. Those are the costs sellers cut first, and you cannot see the cut in a product photo.
The part US buyers get wrong
Importing a counterfeit watch into the United States is illegal. CBP can seize the parcel, and you have no recourse when they do. There is no warranty, no service, and no resale. Independent watchmakers often refuse to touch replicas because parts do not exist. Resale value is zero, and the sites themselves disappear, which makes a chargeback hard to file after the fact.
If what you want is the look
The slim round dress watch silhouette belongs to everyone. Plenty of legitimate brands sell one on a leather strap for less than a replica plus a seized parcel plus a lost payment. A used IWC from a dealer costs more than that, but it holds value and it can be serviced. That is the honest trade.