Platinum Assay & Hallmarking
Look for a full UK hallmark on any platinum item weighing over 0.5 grams. Find out more about how we assay platinum here Birmingham Assay Office.
Platinum Assay & Hallmarking in the UK
Platinum is one of the world’s most valuable precious metals, prized for its rarity, durability, and naturally white appearance. Whether used in fine jewellery, luxury watches, or investment pieces, platinum items sold in the UK must meet strict legal standards of purity. Assay and hallmarking provide independent verification that a platinum item contains the precious metal content claimed by its manufacturer or retailer.
What Is Platinum Assay?
Assaying is the process of testing a precious metal item to determine its purity. Before a platinum item can be hallmarked, it must be independently examined by an authorised UK Assay Office to confirm that it meets the required legal standard.
During the assay process, Birmingham Assay Office specialists analyse the metal content using X-ray fluorescence (XRF) to ensure the item contains the minimum level of platinum declared by the maker. Only items that pass these tests are eligible to receive a hallmark.
How to Identify UK Platinum Hallmarks
Platinum hallmarks are marks applied to precious metal items to confirm their purity and provide information about where and when they were assayed. Understanding these marks can help you verify the authenticity, age, and origin of your platinum jewellery and collectable pieces.
What Is a UK Platinum Hallmark?
A UK hallmark is a series of symbols stamped onto an item made from precious metal. Hallmarking is a legal requirement in the UK for platinum items weighing 0.5 gram and over, and provides assurance that the metal meets the required standards of fineness.
A typical UK platinum hallmark typically contains several key marks:
The Sponsor’s Mark
(Previously known as a Maker’s Mark)
The Fineness Mark
850, 85% Platinum
The Assay Office Mark
Birmingham Assay Office
Step 1: Identify the Platinum Purity Mark
The fineness mark indicates the purity of the platinum. The number represents the parts of pure platinum per thousand.
For example, a hallmark reading “950” confirms the alloy is 950 parts platinum and 50 parts other elements, containing 95% pure platinum. This is the most common fineness for platinum jewellery.
Common UK platinum standards include:
850, 85% Platinum
900, 90% Platinum
950, 95% Platinum
999, 99% Platinum
Step 2: Look for the Assay Office Mark
Every hallmarked platinum item is tested and certified by an authorised UK Assay Office. The assay office mark shows where the item was independently tested and hallmarked.
Each office has its own unique symbol:
Birmingham Assay Office
London Assay Office
Sheffield Assay Office
Edinburgh Assay Office
Step 3: Find the Sponsor's Mark
The sponsor’s mark (sometimes called the maker’s mark) identifies the company or individual who submitted the item for hallmarking.
This mark usually consists of two to four initials within a shaped shield.
Sponsor’s Mark: Birmingham Assay Office
Step 4: Check the Date Letter (If Present)
Many older British items feature a date letter. This alphabetical mark changes each year and can help determine when an item was hallmarked. The date letter was a compulsory hallmark until 1999.
Date letter styles vary between assay offices and different hallmarking periods, so a specialist date letter chart is usually required for accurate identification. You can find ours here.
It did not become mandatory to hallmark platinum until 1975, with the implementation of the Hallmarking Act 1973. While many customers still opt for a date letter mark, you may find both second-hand and contemporary pieces without a date letter.
Date Letter 2026: Letter B
Traditional Fineness Mark for Platinum
Though platinum was not required to be hallmarked until 1975, traditional fineness marks were still compulsory until 1999.
Now an optional mark, British platinum can be identified using the orb, a symbolic standard mark.
Fineness Mark: Platinum
Convention Marks
The Convention Mark is an optional hallmark that indicates a precious metal item complies with the standards of the International Hallmarking Convention, also known as the Vienna Convention. Introduced in 1972, the Convention enables hallmarked items to be more easily recognised and traded between member countries without the need for re-testing or re-hallmarking.
On platinum items, the Convention Mark takes the form of a set of scales either containing the fineness number or alongside the fineness mark. When present alongside UK hallmarks, the Convention Mark provides additional assurance that the item meets internationally recognised standards of purity and has been independently tested by an authorised assay office.
Common Control Mark Type 1: 950 Platinum
Common Control Mark Type 2
Common Misconceptions About Platinum Marks
An Orb Doesn’t Always Mean Platinum
When identifying platinum, it’s important to be aware that there has been another historic orb mark. Introduced as a commemorative mark for the Queen Elizabeth II’s Platinum Jubilee, the mark was available from 1 November 2021 and could be applied up to 31st December 2022.
Designed by Thomas Fattorini Ltd, the orb was chosen to reflect the traditional fineness mark for platinum and contained Queen Elizabeth II’s royal cypher, as well as ‘70’ for 70 years on the throne.
The commemorative mark could be applied to any precious metal alongside the compulsory marks.
Platinum Jubilee Mark: 2021 Mark
What’s Your Treasure Worth?
Here at Birmingham Assay Office, we offer valuations of watches, jewellery and silverware, whether you need them for insurance replacement, probate, family division, private sale or other official purposes. Our expert valuers are experienced and trusted to deliver accurate, detailed valuation reports that are widely recognised by insurers, legal professionals and the trade.