These records are chiefly files of the Director's Office, 1964-1969, 1971-1972. During the earlier period a complicated subject-numeric system was in use. In 1971 a
simpler subject-numeric plan was used and replaced before the end of that year by a straight alphabetic subject file, which is the current office filing system. A full history
of the Director's Office and of its filing systems can be found in Record Unit 155.