First, welcome, and glad you found your way here before worse could happen again.
Always best to remember, what the internet shows you or tells you that you’re going to get, and then you actually getting it, becoming the default way of doing business, is only a relatively recent thing.
We all sometimes need to take that extra moment or several to ask ourselves what those pictures on that website we found because someone of potentially questionable intent paid Google or another search engine to show it to us earlier in the search results, actually means.
Paying Google for search result placement doesn’t render your business legitimate on the internet.
It’s been an awfully long time since I myself flung paper money orders by post across the world to buy goods of questionable character from characters of even more questionable character as a teenager, back around the turn of the millennium.
We trust too much by default at times.
There is no certification body out there who the maker of a rep watch gets a certificate from, because of the nature of the product. You are asking for proof of something which is very hard indeed to prove.
If a group can put together a very good approximation of a watch worth thousands, chances are they can probably also put together a good approximation of any means of authenticating it, too. So a rotating monthly case back sticker used, for example, by the real Clean Factory organisation, only achieves so much. I’ve seen situations of multi layered security credentials which a government agency has spent a lot of money rendering secure - more so than say a drivers licence - defeated by a home hobbyist.
Only by consensus - which this forum provides via the long term and reliable Trusted Dealers - can anyone have a good certainty of getting what they paid for. Outside this framework, you are taking your chances.
All the best, and read, read, and read some more.