Records of the Patent Office relating to the patenting of inventions.
General files of the Patent Office and Industrial Property Department are in BT 209.
Registers of designs under the Ornamental Design Act 1842 and subsequent legislation, giving the registered number of the design, date of registration, type of design, maker's name and address, and possibly the designer's name, are in BT 44, BT 46, BT 48, BT 51 and BT 53.
Representations under the Design Copyright Act 1839 and subsequent legislation, being samples, drawings or photographs of registered articles, are in BT 42, BT 43, BT 45, BT 47, BT 50 and BT 52.
Representations of trade marks from 1876 are in BT 82 and BT 244.
The nineteenth and early twentieth century registers and indexes of patents and trade marks formerly in BT 73, BT 74, BT 75 (patents) and BT 80, BT 81, BT 86, and BT 92 (trade marks) were destroyed in 1963 in accordance with Public Records Act 1958 s6, with the exception of a few specimens transferred to BT 900.