The papers records were transferred from the Admiralty between 1961 and 1977 and are known by their Public Record Office class number, ADM/138. They consist of 650 volumes known as 'Covers', relating to ship design, 1860s to 1939. There are comparatively few volumes for the early years and it is not until the late 1860s that the Covers begin to be comprehensive as a record of design. At the time of writing they do not extend beyond 1939 but it is anticipated that the Museum will hold Covers for later ships. Each cover concerns the design and construction of, and subsequent alterations to, a warship or a class of warships. There are also a number concerned with intelligence reports on foreign warships (grouped by type and nationality), general documents on particular types of ships, while others deal with specific topics, such as underwater protection or refuelling at sea. Fleet auxiliaries and ships' boats are included as well as warships. The form of the cover is a 'guard book' into which are inserted original papers or office copies of the letters, memoranda and minutes on the subject of the volume, which usually includes papers on the development of the design, calculations and correspondence with the builder or builders. The latter will occasionally contain information on contracts. Other subjects include inclining experiments, trial records, information on alterations and refits and, in some cases, extracts from action reports. However, coverage of these subjects is often erratic. Each cover contains an index to its contents. Detailed indexes to the volumes are available in the Draught Room of the Department of Ships.