Short answer: a "fake IW93870" is almost always a replica listing wearing an IWC-style reference number. That exact number does not line up with a documented IWC production model in the usual catalog listings, which is your first clue. If you searched that string, you are most likely looking at a seller page rather than a watch that came out of Schaffhausen.
What the reference number actually tells you
IWC reference numbers follow a house pattern: "IW" plus digits, like IW371617 or IW500705. The digits are not decoration. They tie a watch to a case size, a dial variant, a movement, and a production window. When a listing throws out a number that does not resolve to any of those things, the number is doing marketing work instead of identification work. That happens a lot with replica sellers, who borrow the format because it looks official.
Why the number matters more than the photos
Photos get copied, recycled, and lifted from genuine listings all the time. I treat a reference number as the spine of the listing, because it is the one thing a seller has to keep consistent across every page they post. Cross-check the number against the model it claims to be. If a seller calls it a Portugieser in one photo set and the case shape reads like a Pilot's Chronograph, you already have your answer.
What to look at on a replica actually in front of you
Once you are past the naming problem, the physical tells come down to a handful of things.
- Case finishing. Look at the transition between brushed and polished surfaces. Sharp, wandering lines and rounded edges are the usual giveaway. Genuine cases break cleanly between finishes.
- Dial printing. Text should sit crisp and level under magnification. Fuzzy edges, uneven spacing, and logos that look painted rather than applied are common on cheap builds.
- Movement behavior. Wind it, set it, watch the seconds hand. A movement that stutters when the crown is pushed in or sweeps unevenly is telling you about the whole watch, not just the movement.
- Weight and bracelet feel. A bracelet that rattles or pulls hair usually means stamped links rather than solid ones.
- Caseback engraving. Reference, serial, and model text should be consistent with each other. Replicas often mix a real reference with a serial from a different model.
The US legal picture nobody mentions in the listing
Buying a counterfeit watch in the United States is not a gray area, and it is not a private matter between you and a seller overseas. Counterfeit goods infringe a registered trademark, and US Customs and Border Protection can seize shipments. Personal importation of counterfeit merchandise is prohibited, meaning the package can disappear and you have no realistic route to a refund. Nothing about a "1:1" label changes that.
Rules I would use before spending anything
- Verify the reference against the manufacturer's own published information first. If it does not exist there, everything after that is guesswork.
- Ask for dated, angled photos of the actual piece, not stock images.
- Assume the watch will need servicing, and price that in.
- Accept that resale value for a replica is close to zero, because the secondary market does not authenticate or support them.
If a seller cannot tell you what model the reference belongs to, or gets defensive when you ask, that is the most useful information you will get from the whole exchange.