Table Of Content

• What is a hallmark?
• The Hallmarking Act of 1973
• What is an assay office?
• Traditional fineness symbol
• Millesimal fineness mark
• Date letter
• Common control mark (CCM)
• How to read hallmarks

The hallmark is a mark which shows that the item has been independently tested and verified as matching its description, and conforming to legal standards of purity or fineness of the metal. 

Precious metal such as platinum, gold, palladium and silver are normally alloyed with other metals to achieve a desired strength, durability, colour etc. It is not possible to detect by sight or by touch the metal content of an item. Therefore it is a legal requirement to hallmark articles consisting of platinum, gold, palladium or silver (subject to certain exemptions, see below "The Hallmarking Act of 1973). 

An example of a full set of UK hallmark from London Assay Office:

From left to right:

The first mark is a sponsor's mark, it tells you who submitted the item for hallmarking (compulsory).

The second mark is the traditional fineness symbol,  it tells you what precious metal the article is made of.

The third mark is the millesimal fineness mark, it tells you the quality of the precious metal and the metal type (compulsory).

The fourth mark is the assay office mark, it tells you where the item was hallmarked (compulsory).

The last mark is the date letter, it tells you when the item was hallmarked.

The Hallmarking Act of 1973

In 1973 a new Act of Parliament was passeed to regulate and simplify the law regarding hallmarks on silver, gold and platinum which came into force on 1 January 1975.

Items weighing more than 7.8 grams must be hallmarked before they can be described as silver, for gold it is any item above 1 gram, and for platinum above 0.5 gram. Items before 1950 may be described and sold as precious metal without a hallmark if it is of minimum fineness and was manufactured before 1950.

Assay (from the Old French assai, essay = examination, trial, essay), is the operation of testing the purity of metals. From the earliest period in the history of English goldsmiths, it refers to verifying the amount of pure gold or pure silver contained in any object that is described as "gold" or "silver".

Assay Offices test the purity of precious metals. Only four assay offices remained in Britain by 1975. The assay office mark identifies the town or city where the item was assayed.

These are optional marks that can be added alongside hallmarks but are not compulsory.

This mark tells you the quality of the metal and the metal type of the item. This number indicates the precious metal content of the item, expressed in parts per thousand. The shape of the surrounding shield indicates metal type.

The date letter was compulsory until 1999. The date letter changes once a year on January 1st. It can be applied voluntarily in addition to the compulsory marks. 

Items made from precious metals might have a standard metal fineness (purity) mark known as common control mark.

The UK has been a signatory to the International Convention on Hallmarks since 1972. The presence of CCM indicates that the item has been controlled in accordance with the Convention’s requirements. CCM applied by UK Assay Offices are recognised by all member countries in the International Convention. Conversely, Convention Hallmarks from other member countries are legally recognised in the UK and they do not have to be re-hallmarked in the UK.

The number gives the minimum quantity of the precious metal in the item in parts per thousand. The shape of the control mark indicates the type of precious metal.

Hallmarks on jewellery are usually very small, you will need a magnifier (plus a little bit of patience!) to study it.

Start with the assay office mark to find out where the piece was assayed.

Look at the traditional fineness symbol (if present) to find out the type of precious metal this item is made of.

Now look at the millesimal fineness mark to find out the precious metal content of this item.

If the date letter is present, refer to the correct city's tables to compare and see which letter matches the date letter on your item.

Look up the sponsor's mark to find out the name of the company.

Tips: If the assay office mark is not present, the item probably comes from London.