Guide
How to read a British registered design mark
A British diamond registration mark dates a design registered between 1842 and 1883, not necessarily the object carrying it. Read its material class, day number, month letter and year letter; the layout changed in 1868. From 1884, look instead for “Rd” or “Rd No” followed by a number, then trace that number in the design records.
What the mark proves — and what it does not
A registration mark records the date on which a design was protected. It is not a maker’s mark, a patent, a hallmark or a guarantee that the object was made on that day. The piece cannot pre-date the registration, but a successful pattern might remain in production for years and later examples can carry the same mark.
That makes the date a hard starting point, not a complete attribution. Combine it with the manufacturer’s name, body, construction and decoration before deciding when the particular object was made.
The diamond mark, 1842–1883
The diamond-shaped system was introduced under the 1842 Ornamental Designs Act and abandoned after the 1883 legislation replaced it. Its parts encode the registration rather than spelling it out:
- Material class. A number at the top, usually Roman: I metal, II wood, III glass, IV ceramics, V wallpaper, VI carpets, and VII–XIII for textile classes.
- Day. An ordinary number gives the day of the month.
- Month and year. Two letters use separate code tables. They are not initials, and the alphabet was not used in chronological order.
- Bundle or parcel number. An administrative number that helped locate the registered representation; it is not another part of the date.
The layout changed in 1868. On the earlier form, letters sit on the left side and numbers on the right; on the later form that arrangement is reversed. Do not decode a letter from memory: use the month and year tables in The National Archives’ registered-design guide, which covers both periods and the surviving record series.
How to read it without losing a character
First decide which way up the diamond sits and photograph it square-on in raking light. Then transcribe every position separately: top, centre, left, right and bottom. A worn K can resemble an H and a shallow Roman IV can look like scratches, so record uncertainty rather than forcing the mark to fit a date.
Decode the material class first. It is a useful error check: class IV belongs on ceramics, while class I belongs on metal. If the class conflicts with the object, re-check the orientation and whether the mark is genuinely a registration diamond at all.
Rd and Rd No after 1883
From 1884 the diamond was replaced by a sequential registration number, commonly printed or impressed as Rd, Rd No or Registered followed by digits. The number itself is an identifier, not a date code. It must be matched to the Designs Registry sequence or its surviving record.
The National Archives holds the representations and registers in different Board of Trade series: broadly BT 43 for ornamental designs under the diamond system, then BT 50 and BT 51 for the post-1883 system. Not every entry is fully searchable online, but a clear number, proprietor name and object type can narrow the record considerably.
Do not confuse design registration with a trade mark
A factory name or emblem identifies the business claiming the ware. A registered-design mark identifies legal protection for the object’s appearance. They can appear together and answer different questions. The design may have been registered by a manufacturer, a retailer or a designer; the name stamped beside it may have changed while the registered pattern continued.
On ceramics this distinction matters especially. Read the factory backstamp using the exact trading style, then use the registration mark to establish the earliest possible date. The Staffordshire pottery-marks guide shows how those two strands fit together.
A practical research sequence
- Photograph the whole object and the mark separately.
- Decide whether it is the 1842–1867 diamond, the 1868–1883 diamond, or a post-1883 Rd number.
- Transcribe every character before interpreting any of them.
- Decode the diamond from the National Archives tables, or search the Rd number in the design records.
- Treat that result as the date of the design, then test the object against its maker, materials and method of manufacture.
Common questions
Does a British diamond mark give the exact date of an antique?
It gives the exact registration date of the design, which is the earliest date the object could have been made. It does not prove the manufacturing date. A popular registered pattern might be produced for years, so the factory mark, material and construction still have to agree with the proposed date.
What does Rd No mean on British pottery?
It means the design was registered and the digits identify that registration. The number is not a date printed in code: trace it through a registered-design reference or the National Archives records, then treat the result as the design date rather than an automatic date for the individual pot.
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Last updated: 11 August 2026