I know I am not an authenticator here, and while you wait for
@whateve to reply to you I thought I would add my .02.
You can be pretty assured you are buying authentic from the stores and the brands' website direct.
A retailer is someone like Neimans who sells Valentino but is not the Valentino store. Back in the day I have heard horror stories where buyers would buy chanel or balenciaga from Neimans then return the fake version of the bag to the Neimans, so they get the real bag and their money back. I have no idea how often this happens anymore, or if it all. But, when I buy from a retailer I ALWAYS ask if they have a new bag in the back to sell and then if they do buy the brand new, unopened, bag.
Resale sites are riskier, and I have purchased 2 past season
gucci bags from one online resale site because I felt assured by the pics that they were authentic. There are people who can help you authenticate off these sites.
Buying from Gucci.com is safe, and you should not worry about this. Again, could be some super swapper out there, but they have a return policy and if you felt unsure you could return.
hope this helps