A Guide to Hallmarks

What is Hallmarking?

Precious metals (gold, silver, platinum) are rarely used in their purest forms; they are usually an alloy of the pure metal and another metal. This is what allows your jewellery to have strength and durability. These combinations of metal can then be tested through the ‘Standard Mark’ to check how pure the metal is, known as its ‘fineness’. 

The UK is the only country that hallmarks precious metals by law, assuring high quality and traceability of an item. Jewellery is sent to one of four Assay Offices where it is independently checked and hallmarked.

Where can I find the Hallmark?

Hallmarks are usually stamped inside of rings, and on bracelets they’re often stamped on the clasp. On most items there will be three hallmarks - a Sponsor’s Mark, an Assay Office Mark and a Standard Mark. There are also special Commemorative Hallmarks that can be added in addition to this. 

Types of Hallmark

Sponsor’s or Maker’s Mark

A Sponsor’s or Maker’s mark represents the company or individual that submitted your jewellery for hallmarking at the Assay Office. Each jeweller across the UK has a different Sponsor’s mark with different initials meaning you can almost always trace it back to the original source. All Sonkai jewellery will be stamped with ‘CLS’ meaning it was made by our goldsmith, Craig Snape.


Assay Office Mark

There are four Assay Offices in the UK where every article is independently tested and hallmarked - London, Birmingham, Sheffield and Edinburgh. Each of these offices has a unique hallmark meaning it can be traced back to where the metals were first tested. Sonkai use the London Assay Office meaning all items will contain a small leopard hallmark.

Commemorative Hallmark

Platinum Jubilee Hallmark

Every order placed at Sonkai between now and the end of the year can be marked with the official Platinum Jubilee Hallmark. This limited edition commemorative Hallmark is only available to be used until the end of 2022, making this an extraordinary opportunity. Designed by Thomas Fattorini, the mark depicts ‘EIIR’ over the number 70 within a small orb and has been sanctioned by The British Hallmarking Council.



Standard Mark

This mark shows the purity of the metals in the piece in parts per thousand. Each metal has a different shaped mark. The number shows the lowest standard found when the metal was tested, meaning your jewellery will not be less fine than the number on the hallmark.







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EMAIL: mail@sonkai.co.uk