Hallmarking at Sayers London

What is a Hallmark?

A hallmark is an official mark applied to items made from precious metals — including gold, silver, platinum, and palladium — to certify their purity. At Sayers London, every hallmarked piece has been independently tested by a UK Assay Office to ensure it meets the legal standards for metal fineness. It’s your assurance of authenticity, quality, and trust.

Sayers London is part of Jewellerybox Ltd, which is an Assay Assured jewellery retailer

It is a legal requirement to hallmark all sterling silver items which weighs over 7.78g and all 9ct gold jewellery weighing over 1g, which we strictly adhere to. Hallmarking ensures that our customers feel confident knowing that their jewellery is made from what we say it is.

What other marks might you see on your precious metal items?

You may notice that some of our items have a 925 or 375 stamp. These stamps are applied by some manufacturers, and although indicative of the metal purity, are not full UK hallmarks. Many of our pieces are stamped rather than hallmarked, as the majority of our pieces are quite dainty and light, and therefore do not meet the requirement for a hallmark. We try to keep our stamps and hallmarks pretty small so that they do not affect the look of the jewellery, so you might have to look closely to see it. Regardless of whether the item has a UK Hallmark or not, it is still guaranteed to be the purity stated.

What do "925" and "375" stamps mean?

As well as being stamped on certain low-weight items, you may see these numbers in our descriptions and specifications. Sterling silver, marked with “925”, contains 92.5% pure silver, balanced with 7.5% other metals (usually copper) to enhance strength and durability. While higher-purity silver exists, it’s far softer and more prone to scratches and dents. That’s why 925 sterling silver is the standard for fine jewellery: it offers the perfect blend of beauty, quality, and resilience.

"375" is the same principle, but for 9ct Gold. 9ct Gold is 37.5% pure gold, blended with other alloys to enhance strength and durability. While it contains less pure gold than higher carat options like 18ct or 22ct, 9ct gold offers a beautiful balance of affordability, resilience, and long-lasting shine — making it a popular choice for everyday jewellery.

What is the Assay Office?

The Assay Office is an official institution responsible for testing and certifying the purity of precious metals such as gold, silver, platinum, and palladium. In the UK, only the Assay Office can apply a legal hallmark, confirming that an item meets the required standards for metal fineness. This independent verification gives you confidence that your item is exactly what it claims to be — genuine, tested, and fully compliant with UK law.

The 4 assay offices are independently run and each charges customers to have their items marked. The assay offices are overseen by the British Hallmarking Council (BMC) and each assay office is represented by 1 or 2 councilors on the BMC with optional the addition of two co-opted members outside the assay offices. The BMC is funded completely by the assay offices.

Sayers London, as part of Jewellerybox ltd, uses the Edinburgh Assay Office - you may see their stamp on your item, a three-towered castle. The other Assay offices are based in Sheffield, London and Birmingham