A very expensive piece can be a bad heirloom and a modest one can be a superb one, because the qualities that make jewellery last are not the qualities that make it costly. Cost is driven mostly by stone weight. Survival is driven by setting, metal and form. So a large stone in a delicate claw setting is expensive and fragile, and a small stone in a heavy bezel is cheap and close to indestructible. Both of those sentences surprise people. The second thing price does not buy is repairability. A piece assembled with glue, or built around a proprietary clasp, or made in a way that cannot be resized without destroying the pattern, is a piece with a shelf life regardless of what it cost. Ask one question at the counter. Can this be repaired, and by whom. A jeweller who answers easily is telling you the construction is conventional, which is what you want in something you intend to keep.

Start with the metal stamp. Solid gold is marked, and the mark tells you the alloy. Then look at how the stones are held. Bezel and channel settings protect the stone and survive daily wear. Claws and prongs show the stone better and need checking every few years, which is fine if you know to do it. Then look at the joins. On a chain, the clasp and the last few links are where failure happens, and a heavier clasp on a light chain is a good sign rather than a clumsy one. Then look at the back. Finished, smooth, and marked on the reverse is the mark of a piece made to be handled. Rough or unfinished on the reverse means the piece was made to be photographed. Finally, consider whether you would recognise the design if you saw it with no branding. The pieces that hand down well tend to be legible on their own.

There is a version of this conversation that is really about status, and we would rather have the useful version. The honest answer is that a plain heavy gold band, bought at a fraction of the cost of a statement piece, is more likely to be worn by someone in fifty years than almost anything else you could buy. That is not a romantic answer and it is the true one. If you want a stone, put the money into the setting rather than the carat, and buy the smaller stone. If a piece cannot be resized or repaired, treat it as a pleasure rather than a legacy and price it accordingly in your own head. And do not buy an heirloom for someone whose taste you do not know. If you take one thing away, look at the back of the piece, because that is where the maker stops performing.