1. Why use this guide?
1.1 Diamond Marks 1842-1883
Use this guide if you are trying to find out about an item with a diamond mark but you don't have the registered design number.
The diamond mark, found on the item itself, can help you to work out when it may have been manufactured and what material class it belongs to. This information can help you in searching for a design registration, but you should note that not all searches will be successful.
See our research guide on registered designs for more information.
1.2 Trade marks 1876-1938
Use this guide to find original representations (drawings, paintings, photographs) of trade marks.
The National Archives collection is far from complete, but this guide will suggest supplementary sources for researching trade marks.
2. Essential information
2.1 Diamond marks
Diamond marks were issued by the Patent Office between 1842 and 1883. They were issued with the registration number when a design was registered.
A diamond mark showed that an item was designed in Britain and the design had been registered. It also meant that the person registering it had legal protection against others copying it.
2.2 Trade marks
Trade marks were used to identify a brand. A company's trade mark made their goods recognisable and assured comsumers of the quality they could expect from a product.
Cotton trademarks were registered in Manchester and non-cotton trademarks in London.
Trade marks are still used to protect brands. The ® symbol shows a trademark has been registered. The ™ symbol indicates a manufacturer considers the mark to be a trade mark but it has not been registered
3. What do diamond marks look like?
Diamond marks were printed, engraved or otherwise marked on a design - for example on the underside of china or the reverse of printed fabric.
The mark was in the shape of a diamond with numbers and letters marked at specific points to represent:
- the type of material used (known as the class)
- how many items were included (sometimes known as bundles or packages)
- the day, month and year of registration
4. What do trade marks look like?
The purpose of a trade mark is to be a recognisable symbol of a specific manufacturer - so they are designed to be distinct. Traditionally they have been:
- a word written in a particular style and colour such as Rose's cordial or Pears' soap
- a made up word such as Lego or Vaseline
- a more detailed image such as the lion used by MGM or the Burberry check pattern
More contemporary trademarks include symbols or icons such as those used by Nike and Apple, and sounds or jingles such as the Intel and Nokia tunes.
5. How to interpret a diamond mark
Diamond marks included a letter code to represent the year the design was registered. By the end of 1867 the alphabet had been used in full and the diamond mark had to be altered to avoid repetition.
This means that the letters and numbers used to represent dates are at different points of the diamond between 1842-1867 and 1868-1883.
The mark at the top of the diamond was a Roman numeral representing the material the item was made from. These did not change position.
Use the examples below to work out which date range corresponds to the diamond mark on your item.
For example, if you have a letter in the left point of the diamond and a number on the right, then it falls into the 1842-1867 range. If the number is on the left and the letter on the right it is in the 1868-1883 range.
Use the tables below to work out what the codes represent for the date and the class of material.
6. Diamond mark month codes
|Month code||Month||Month code||Month|
*R was used during 1-19 September 1857
*K was used for December 1860
*G was used for the month in place of W 1-6 March 1878
7. Diamond mark year codes
7.1 Year codes for 1842-1867 in alphabetical order
|Year codes||Year codes||Year codes|
7.2 Year codes for 1868-1883 in alphabetical order
|Year codes||Year codes|
*From 1-6 March 1878, W was used for the year in place of D
7.3 Codes listed chronologically
|Year codes||Year codes||Year codes||Year codes|
*From 1-6 March 1878, W was used for the year in place of D.
8. Material classes
VII-XIII Textiles of various kinds, including dress and furnishing fabrics
9. Using our catalogue to find records of trade marks
Records of trade marks are in record series BT 82, BT 900 and BT 244 (see section 7 for more information). The trademarks are not individually described in the catalogue. Instead, they are listed in ranges of registration numbers.
If you know the registration number you can browse the relevant record series in the catalogue to find the right range. For example, if you are looking for registration number 20300, you will find it in BT 82/82 which has the range 20251-20500.
Using the advanced search option to search the catalogue within specific record series and dates will give you more focused results.
Our catalogue contains descriptions of our records. None of the records described in this guide are available online. To view the documents that you find references for, you will need to either visit The National Archives at Kew or pay for copies to be sent to you. Alternatively, you can pay for research.
10. Trade mark representations and registers
When a trade mark was registered, two types of record were created.
A representation (for example a painting, sketch or photograph) of the trade mark was submitted and pasted into a book along with a registration number shown on the same page. Sometimes the manufacturer's details are written onto the same page - but not in all cases.
The National Archives has representations in record series BT 82 (1876-1938) and BT 244 (1876-1922). The record series descriptions in the catalogue give useful administrative histories that will help you to understand how the records were created.
BT 82 includes representations for cotton and non-cotton classes from both London and Manchester offices.
BT 244 contains representations of trade marks for cotton classes from Manchester only. A number of files were destroyed by enemy action in the Second World War.
The files are arranged according to the material class of the items - so that:
- BT 244/1-44 are class 23
- BT 244/45 - 436 are class 24 (and numbers begin with M)
- BT 244/437-461 are Class 25
Search the catalogue within BT 82 and/or BT 244 by date to find the volume of representations that will cover the trade mark you are looking for.
Once the representation was received and given a number, an entry was made in a register along with details of the manufacturer or company registering the trade mark.
Unfortunately only a few specimen registers, all relating to BT 82, survive. They are in BT 900 as follows:
- BT 900/15 register of trade marks covering 5 October 1876
- BT 900/16 register of trade marks covering 3 October 1876
- BT 900/17 register of trade marks covering 1884
- BT 900/18 register of trade marks covering 1934
- BT 900/19 Appendix to registers of trade marks covering 10 November 1933 to 11 December 1935
- BT 900/20 Indexes to registers of trade marks covering 15 Jan 1884 to 3 October 1884
There are no registers for the representations in BT 244 making it difficult to link a trademark to its owner unless details were written in the representations volume.
11. Other useful sources for trade marks
The Intellectual Property Office (IPO) now has responsibility for registration of trade marks. Search the IPO database to find trade marks by name of company or description of trademark. If you find the registration number this way you can then look for the original representation in our records.
The British Library has a collection of the Trade Marks Journal from the first year of publication in 1876. The British Library website also offers further guidance on patents, trade marks, designs and copyright.
The publication 'A Century of Trade Marks 1876-1976' (HMSO 1976), available in The National Archives library, gives a detailed explanation of:
- the Acts of Parliament relating to trademark registration
- how the records were created
- the systems used to allocate numbers to registrations
Search our catalogue using the terms trademark and trade mark (both terms are used frequently) and filter your results to see what is held in other archives.