Ebay basicly works on the positive/negative feedback system. Ebay has policies regarding selling "fake" items esp when it is said in the item description that it's authentic!
If you seriously want to purchase something like a "tiffany"-- I'd do some investigating of their feedback (if they have any negatives), and if the seller will allow returns & has some sort of guarantee. Be weary of "fishy" and vague descriptions.
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