Victorian silver plated table candelabra late 19th century, by Thomas Bradbury & Sons, Sheffield, diamond registration mark Palm tree design column, supporting three sconces. Height 52 cm
registered design. During the period 1842-1883 the Patent Office issued a diamond mark along with the registration number when a design was registered.
Besides indicating that the design had been registered, a diamond mark offered the buyer the reassurance of knowing an item was of British design. It assured the person registering the design a degree of protection from copying.
The mark was created to identify the type of material used (known as the class), how many items were included, (sometimes known as bundles or packages), and the date of registration.
On the diamond mark the year of registration is shown along with the month code. However, there are two ranges of year codes; 1842-1867 and 1868-1883. By looking at the design of the diamond mark you should be able to determine the correct year from the design of the diamond mark and the placing of the day number.
Source and further information: http://www.nationalarchives.gov.uk/records/research-guides/reg-design-diamond.htm
The buyers premium is an additional percentage charge on the hammer price of the item, imposed by the auction house to cover administrative costs. The buyers premium percentage varies between auction houses, with a range of 12.5% to 22%.