The vintage engagement ring buying guide

Most people arrive with a picture. It is more useful to start with the era, because the era decides the proportions, the metal and the way the stone will look on a hand.

Antique diamonds were cut by eye to be seen by candlelight. An old European cut has a small table, a high crown, a large open culet and broad facets that throw big, slow flashes of color rather than the fast white sparkle of a modern brilliant.

Graded against modern standards, an old cut will almost always score lower for cut. That is a scoring artifact, not a fault. Antique diamond pricing is not directly comparable to modern certified diamonds. Cut, rarity, condition, provenance, color, clarity and the originality of the mounting all affect value.

Ask whether the center stone is original to the mount. A period stone in a period ring is worth more than a modern stone dropped into an old setting, and any honest seller will tell you which you are looking at.

This is where a vintage ring is either a wonderful buy or a slow disappointment. Ask for these numbers before you pay.

A plain shank can usually be sized two sizes either way without touching the design. A fully engraved, milgrained or eternity-set band often cannot be sized without destroying part of the pattern, and the honest answer there is to buy the right size or accept a visible repair.

Full-circle eternity bands and calibre-set shoulders are the hardest of all. If a ring like that is not your size, we would rather tell you than take the order.

You should receive, at minimum, a written description of the metal and its karat, a stone description with approximate weights, a statement of the period and any known repairs, and an insurance valuation.

For a US buyer, also confirm how the piece is shipped, whether it is insured door to door, and whether import duties are already paid. On our own pieces they are: the price you see is the price you pay, with no collection at your door.

Photographs flatten stones and hide wear. Before you buy at a distance, ask for a video viewing where someone turns the ring in daylight, shows you the back of the setting, the inside of the shank and the hallmark, and answers questions live.

That single call replaces most of the risk in a remote purchase, and it costs nothing. Combine it with a proper return window and you are in a stronger position than most people buying in a store.