You may have heard of hallmarks, but like me before I started making jewellery, may not understand the rules around when they are needed.

A hallmark is a set of marks applied to an article by an Assay Office (I’ll come back to that!). A hallmark provides an independent guarantee of precious metal purity. And it offers valuable customer and consumer quality assurance. It’s also a legal requirement when selling precious metal items over a certain weight.

A hallmark is made of the following individual marks

• Sponsor’s mark: who made the article or submitted it for hallmarking (compulsory mark)

• Traditional fineness mark: what the article is made of (optional mark)

• Millesimal fineness mark: what the article is made of and its purity (compulsory mark)

• Assay Office mark: where the article was hallmarked (compulsory mark)

• Date letter mark: when the article was hallmarked (optional mark)

  There are 4 Assay offices in the UK and my Hallmark is held at the London Assay Office, Goldsmiths Hall. This is the place I send my jewellery to be checked and stamped. Creating and having my own sponsors mark (makers mark) is a wonderful piece of tradition as well as a legal requirement for silver over 7.78 grams.

  The silver weight does not include any detachable parts (like chains) or the weight of any sea glass. I weigh each piece before setting the sea glass or pottery to see if it will need a hallmark.

  The threshold for sterling silver is quite high compared with other metals so this means that only a few on my items require hallmarking, for example bangles and occasionally a particularly large pendant. If the piece is under 7.78 grams I do not have it hallmarked, however it is made from the same recycled sterling silver and fine silver purchased from Cooksons Gold a reputable supplier to jewellers.

If you are interested in finding out more about hallmarking please visit the Goldsmiths’ Company Assay Office website.

Hallmarks are important as precious metals, such as gold, silver, platinum and palladium, are rarely used in their purest form. They are mixed with other metals to form an alloy that has the desired colour and strength. It is very difficult to know what an item of jewellery is made of just by looking at it or touching it. Hallmarking protects consumers by certifying the precious metal content of the piece so that the buyer knows that the item is genuinely what the seller says it is.

Online selling of jewellery increases the risk to consumers, but the hallmark gives the buyer confidence that the products are genuinely what they say they are.

If a precious metal item weighs less than a certain amount it is not compulsory to apply a hallmark. The minimum weight thresholds are:

• gold 1 gram

• silver 7.78 grams

• platinum 0.5 gram

• palladium 1 gram

If you are sold an item of jewellery made with gold, silver, platinum or palladium over the minimum weight and it is not hallmarked, then the seller is breaking the law.