Authenticity cannot be settled on a video call, and this is the one category where that sentence is about safety rather than money. A counterfeit cosmetic goes on skin.
What to ask them to show
The batch code and any printed date, photographed in focus. Then look it up yourself before bidding.
The seal, close up, and whether it is intact.
The base of the container and the outer carton, both.
Asked outright: has it been opened, used, or swatched?
Where it was bought and when. For anything with a shelf life, when matters as much as where.
What a refusal means
A batch code is printed on the item and takes one photograph. A seller who will not photograph it, on a product class that is counterfeited as heavily as this one, has declined the only check available to you.
"It is sealed so it must be genuine" is not an argument. Sealing is not hard to do.
What this page will not do
It will not describe how counterfeit packaging differs from real packaging. This category is targeted hard and the copies are good, and a buyer comparing a photograph to a general description is not performing a check.
And the honest advice here is different from every other page in this set: for anything that goes on skin or in a body, the uncertainty may simply not be worth it at any price.
What protects you if you get it wrong
A counterfeit is not as described: returnable for 7 days whatever the store's policy says, and reportable.
Note also that some things cannot be resold at all, and that opened cosmetics raise hygiene rules a store has to follow. If a listing is vague about whether something has been used, treat that as the answer.
Questions people ask
Is it safe to buy cosmetics second-hand?
Unopened and in date, many people do. Opened is a different question and a store has to be explicit about it.
What if the batch code does not come up?
Then you have learned something useful. Ask the seller before bidding.
Does Metzee check these?
No. We do not handle items. Counterfeits are banned and reports are acted on.
More: spotting a counterfeit before you bid, Metzee's position on counterfeits, reporting a seller, questions to ask before bidding on beauty products.