Once upon a time, I worked on behalf of a few luxury goods makers, tracking down counterfeit versions of their items, and getting the obvious and less obvious fakes removed before anyone could waste money (and their perception of the brand) on them. A few times, I would be invited to company HQ and introduced to the product, have the stitching and design details explained to me, a lay humble scruffy programmer. I can…
The most difficult fakes are those illicitly made by the same factory that makes the genuine product (under license). In that sense, they are not even fakes but the license holder doesn’t see any of the profit.
On the plus side, the factory faces a problem as the consequences of being caught are severe. They’ll often take mitigating action to try and obfuscate the source, such as using slightly different materials so eg leather stock can’t be traced. When I was in the industry, it’d be unusual for a factory to produce the exact same thing without _any_ attempt to hide.
If you’ve ever seen a dvd with the various identifiers sanded off, now you know why :)