Authenticity cannot be settled on a video call, and in this category that matters more than in any other, because the gap between what a thing looks like and what it is worth is widest here.
What to ask them to show
The hallmark, under magnification, in focus. Ask for it even if you cannot read it — a photograph of it is something a jeweller can read later.
The piece on a scale, on camera. Not a stated weight; the reading, happening.
Any papers, certificates or receipts, photographed in full rather than described.
For a watch: the movement, if the case opens, and the dial under angled light rather than straight on.
For a stone: it out of its setting if that is possible, and if it is not, say so plainly in the description.
What a refusal means
Reassurance instead of a reading is the thing to notice. "It is solid gold, I have had it for years" is a sentence, not a weight.
A seller who will not weigh something on camera is telling you something, and it takes thirty seconds with a kitchen scale.
For anything claiming to be a known maker, ask where it came from and when. A vague provenance is not proof of a fake; a refusal to discuss it at all is worth your attention.
What this page will not do
It will not tell you what a genuine marking looks like, or what a given purity ought to weigh. Those specifics are exactly where a confident page does damage: a buyer who has "checked the hallmark" against something they read on a blog is in a worse position than one who knows they have not checked anything.
For anything expensive, the honest route is a photograph good enough for a jeweller, and then a jeweller.
What protects you if you get it wrong
An item sold as gold that is not gold is not as described, which makes it returnable for 7 days whatever the store's policy says, and reportable.
This is also the category where a lost parcel is a serious claim rather than an inconvenience, so ask how it will be sent and whether it is insured before you bid.
Questions people ask
Can Metzee test a metal or a stone?
No. We do not hold the item at any point and we do not authenticate.
Is a hallmark enough on its own?
A photograph of a hallmark is evidence for somebody qualified to read. It is not a verdict you can reach from a show.
Should I buy expensive jewellery live at all?
Many people do, successfully, by treating the show as the place to gather evidence rather than the place to be convinced.
More: spotting a counterfeit before you bid, Metzee's position on counterfeits, reporting a seller, questions to ask before bidding on jewellery or a watch.