The most familiar manifestation of the OR map is of course the modern map catalogue index map but this is a specialist use of the OR designation. OR maps existed in their own right prior to the adoption of the OR designation for indexes. The OR designation was generally applied to small-format simple outline sketch maps, often monochrome used for a multitude of purposes. They are not without interest however. One use that comes to mind was that of the 3 or four Office Reference maps used to illustrate the stages of the retreat from the Thai border down through the Malay peninsula and onto the island of Singapore in 1942 that were produced presumably for high level briefing purposes.