Complete Hallmark and Metal Guide

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The purpose of this document is to give practical guidance in relation to Hallmarking matters. The UK Assay Offices are happy to answer questions arising from this information.

Selling Precious Metal Jewellery in the UK

Traders who wish to sell precious metal jewellery, ie Platinum, Gold or Silver in the UK must follow the rules laid out by law in the Hallmarking Act 1973.
If these rules are not followed Trading Standards Officers have the right to seize goods immediately and the seller is committing an illegal act.

Why is the Hallmark important?

For the manufacture of jewellery and silverware precious metals are not used in their purest forms. Instead they are mixed with other metals like zinc and copper, known as base metals.
The resulting mixture is what is called, an alloy. This is done to give greater strength, durability or a particular colour to the metal.

It is not possible to discern by sight or by touch how much precious metal, if any, is present in an alloy. It is therefore a legal requirement, in the UK, to hallmark all articles consisting
of gold, silver or platinum (subject to certain exemptions) if they are to be described as such.

Precious metal is expensive. If you buy an item which contains less precious metal than it should, then you are being cheated.
The hallmark is your guarantee so you know what you are buying.

It is an offence under the UK Hallmarking Act 1973 for any person in the course of trade or business to:

    •    Describe an un-hallmarked article as being wholly or partly made of gold, silver or platinum.

    •    Supply or offer to supply un-hallmarked articles to which such a description is applied.

How is the precious metal content of an alloy measured?

Gold alloys are graded by carat. The higher the carat, the greater the proportion of gold is in the alloy, up to a maximum of 24 carat (pure gold).


The diagrams above illustrate the percentage of precious metal that should be present in some of the more common precious metal alloys used in jewellery. 
In a hallmark the precious content is expressed in parts per thousand, e.g. 375, 750, 925 etc

What needs to be hallmarked?

Any article described as being wholly or partly made of gold, silver or platinum that is not covered under exempt articles.

Main Exemptions:

Articles below a certain weight are exempt from hallmarking. The exemption weight is based on the weight of the precious metal content only, excluding, for example,
weight of diamonds, stones etc., except in the case of articles consisting of precious metal and base metal in which case the exemption weight is based on the total metal weight:
    •    Gold 1.0 grams
    •    Silver 7.78 grams
    •    Platinum 0.5 grams

What does a Hallmark look like?

A hallmark can only be applied by an independent Assay Office.
A Hallmark is made up of 3 compulsory symbols:

1.  The Sponsor’s or Maker’s Mark

This indicates the maker or sponsor of the article. In the UK this mark consists of at least two letters within a shield. No two marks are the same.

2.  Metal and fineness (purity) Mark

Indicates the precious metal content of the article and that it is not less than the fineness of the article indicated. The fineness is indicated by a millesimal number and the metal type is indicated by the shape of the surround.

3.  Assay Office Mark

 Indicates the particular Assay Office at which the article was tested and marked. There are now 4 Assay Offices in the UK - London, Edinburgh, Birmingham and Sheffield.

Sponsors or Makers Mark

Metal and Fineness (purity) Mark*


Assay Office Mark

* The Hallmark guarantees that the purity of the metal is at least that indicated by the Fineness Number.

There are also a range of optional symbols that can be applied alongside the Hallmark. These are:

Traditional Fineness Symbols


Prior to 1999, silver and platinum fineness were indicated by symbols.

The Date Mark

2000     a               2001                   2002    c               2003    d               2004    e              

2005     f               2006     g               2007    h                2008    j               2009    k              

2010     l               2011    m               2012    n               2013    o               2014    p             

2015    q               2016                   2017    s                2018     t               2019    u              

2020    v               2021    w               2022    x               2023    y                2024    z

The date letter is optional in addition to the compulsory marks. The date letter changes once a year on January 1st.
For earlier date letters check with the relevant Assay Office. Birmingham, Edinburgh etc

The Common Control Mark

The UK has been a signatory to the international Convention on Hallmarks since 1972. This means that UK Assay Offices can strike the Convention Hallmark which will then
be recognised by all member countries in the International Convention. Conversely, Convention Hallmarks from other member countries are legally recognised in the UK.
Articles bearing the Convention Hallmark do not have to be re-hallmarked in the UK. The outline of the mark varies according to the type of Precious Metal.


Three things to remember

Remember that if the mark does not have at least these three symbols then it is not a hallmark. In many cases the manufacturer may stamp a number inside to
state the purity. This is not a hallmark.

Look for a statement in the item description that the item is hallmarked. Don’t be afraid to ask the seller if their products are hallmarked.

If you purchase jewellery without a hallmark there is no guarantee that what you have purchased contains any precious metal at all.


If you have any queries about hallmarks, you can contact any of the Assay Office of Great Britain:

London Assay Office
Goldsmiths' Hall
Gutter Lane
London  EC2V 8AQ
Tel: 020 7606 8971   Fax: 020 7814 9353

Birmingham Assay Office
PO Box 151
Newhall Street
Birmingham  B3 1SB
Tel: 0121 236 6951    Fax: 0121 236 9032

Sheffield Assay Office
Guardians' Hall
Beulah Road, Hillsborough
Sheffield  S6 2AN
Tel: 0114 231 2121    Fax: 0114 233 9079

Edinburgh Assay Office
Goldsmiths Hall
24 Broughton Street
Edinburgh  EH1 3RH
Tel: 0131 556 1144    Fax: 0131 556 1177 






1 Troy Ounce = 31.1035 grams     
1 Ounce pure Gold = 31.1 grams 24 ct (0.9999%)     
1 Ounce (1 Troy) 9ct gold bracelet weighing 31.1gms     
contains (9/24)*31.1 = 11.66gms pure gold     
Therefore (30.1 - 11.66) = 19.44 grams in every Troy Ounce is not gold 


Gold Content by
GOLD       Parts/1000  Gold Content / Troy oz
  9ct                    375                  11.66 gms
  14ct                  585                  18.14 gms
  18ct                  750                   23.33 gms
  22ct                  916                   28.51 gms
  99% pure          990                   30.79 gms
  99.9% pure       999                   31.07 gms
  24ct 100%       1000                   31.104 gms 


Inch     cm      Comment

  16        41       Short Chain for Pendants
  18        46       Standard Ladies, Small Gents
  20        51       Long Ladies, Standard Gents
  22        56       Long Pendant and Lockets
  24        61       Long
  28        71       Very Long
  30        76       Extra Long


 UK        mm Dia    mm Circ          US

  A            11,5           36,25               0.5
  B            12,3           38,64               1
  C            12,7           39,9                 1.5
  D            13,1           41,15               2 
  E            13,5           42,41               2.5 
  F            13,9           43,67               3
  G            14,3           44,92               3.25
  H            14,7           46,18               3.75
  I             15,1           47,44               4.25
  J             5,5            48,69                4.75
  K            5,9            49,95                5.25
  L            16,3           51,24               5.75
  M           16,7           52,46               6.25
  N           17,1            53,72               6.75
  O           17,5            54,98               7
  P           17,9            56,23               7.5
  Q           18,3            57,49               8
  R           18,7            58,75               8.5
  S           19,1            60,0                9
  T           19,5            61,26               9.5
  U           19,9            62,52              10
  V           20,3            63,77              10.5
  W          20,7            65,0                11
  X            21,1            66,29             11.5
  Y           21,5             67,51             12
  Z           21,9             68,77              12.5

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