Introduced by the British Copyright of Design Act 1842, these "lozenge" or "diamond" marks contained coded information about the date and material of the registration.

In 1884 these diamonds were replaced by a simple sequential number. 

For collectors and researchers, the registration number or diamond mark is particularly valuable because it provides a firm date for the first registration of the design ( though the pattern or shape may have continued in production for many years afterwards).

The Act:

The Copyright of Designs Act 1842 (also known as the Ornamental Designs Act) was a landmark British law that formalised the protection of industrial and decorative designs. It replaced earlier, limited laws that mainly covered textiles, extending protection to a wide range of manufactured goods.

The Act aimed to encourage British industrial innovation by providing a formal legal shield against "piracy" (unauthorised copying).

Key Provisions:

• Broad Coverage: It applied to any new and original design used for "ornamenting any article of manufacture," including metals, glass, ceramics, and wood.

• Classification System: Articles were divided into 13 distinct classes based on material (e.g., Class 1 for metals, Class 4 for earthenware).

• Protection Terms: The length of copyright varied by class, generally offering three years of protection for most articles including earthenware. 

• Registration Requirement: For a design to be protected, it had to be registered with the newly
  

How long did registration protection last?

Under British design registration law, protection was granted for an initial period of five years from the date of registration. It could then be renewed in further five-year periods, up to a maximum of twenty-five years.

After the protection period expired, the design became free for other manufacturers to copy and use.

For collectors and researchers, the registration number or diamond mark is particularly valuable because it provides a firm date for the first registration of the design (though the pattern or shape may have continued in production for many years afterwards).

This distinction is important in cases where ownership of a design, its renewal, or its later use by another manufacturer became a matter of dispute.

Questions of registration and legal protection were not merely matters of record, but could lead to disputes between manufacturers. 

An example of how design ownership and registration rights could become disputed can be seen in the case of F. Winkle & Co. 
The case concerns a the shape of an ewer produced by F. Winkle & Co Ltd, which was copied by another manufacturer and the right to use the design became the subject of legal and commercial disagreement.

the registration number 554111 is cast-in on the bottom of the ewer, together with a printed F. Winkle & Co Ltd printed mark

'ELITE' is the name of the pattern

Day - Right hand corner of the diamond -  this is self explanatory

Month - Left hand corner -  this is worked out from the code below:-

Exception Notes:

In 1857 the letter R as a month letter was used during 1-19 September, and during 1860 the letter K was used for December.

Year - Top corner -  this is worked out from the code below (they are listed in alphabetical order):-

Day - Top corner of the diamond -  this is self explanatory

Month - Bottom corner -  this is worked out from the code below:-

 Year - Right corner  -  this is worked out from the code below (they are listed in alphabetical order):-

Exception notes:

From 1-6 March 1878, W was used for the year in place of D; and G was used for the month in place of W.

Exception Notes:

In 1857 the letter R was used during 1-19 September, and during 1860 the letter K was used for December. From 1-6 March 1878, W was used for the year in place of D; and G was used for the month in place of W.

Details of the registrations are held at: - 
    
The National Archives, Kew, Richmond, Surrey, TW9 4DU. Tel: +44 (0) 20 8876 3444.

Representations and Registers of Designs, 1839 - 1991

"A representation is a sample, picture, photograph or sketch of the registered design. The registers of designs include the allocated registered number, usually the name and the address of the owner of the design (who was not necessarily the designer), and the quantity of items registered, known as the bundle or parcel. The National Archives holds the surviving representations and registers of designs between 1839 and 1964. These documents are often very large, unwieldy and very dusty: They also have fairly complicated reference systems."