I have no interest in owning anything Hermès. Therefore I have no source for preloved Hermès.Not mad at all at this answer.
There are super fakes everywhere but there are reliable resellers and you can add a layer of security via authentication services.
That being said, have you found better sources / regions in which to buy preloved Hermes? I’m not an Hermes fan so I can’t help OP on this one.
Japan has been the place where they f.e. treat the vachetta on AAA fake LV bags with different chemicals to patina it to make it look older and use professional tools to get leather/canvas to look old. The receipts and documents are copied from a real bag's and they use a real (LV, Chanel, Hermès etc) bag as an example to make a crapton of copies with the exact same markings and then age the bag.
That's way better/worse than just AAA fakes as they are much harder to authenticate than a new bag.