Sub-series consists of records from the registry system known as the Third Central Registry system (5000 block). The records contains the core subject files of Immigration headquarters in Ottawa that were active between 1966 and about 1977. This records system superseded the second Central Registry system (500 block) on April 1, 1966 and was replaced by the fourth Central Registry system (8000 block) in about 1977, although material continued to be added to the old files until 1979. The 5000 block thus contains records on most of the activities of the Immigration Division of the Department of Manpower and Immigration, from the time it was established in 1966 up to its replacement by the Immigration and Demographic Policy Group of the new Canada Employment and Immigration Commission in 1976-1977. There are also a few records of earlier date from previous filing systems, especially the second Central Registry (500 block).
The subjects covered are similar to those in the previous Second Central Registry system. They include immigration law, policy and procedures both generally and in specific fields; the organization and administration of the Division, its Canadian field offices, and to a limited extent its overseas posts; liaison with other federal and provincial government offices, foreign governments, and private organizations; reference files on immigration history and statistics; and a variety of related matters.
No individual case files are included in the Headquarters 5000 block files (although similar series created in Canadian field offices do contain case records). Many of the subject files do, however, contain incidental documentation on specific cases.
Files in the 5000 series are numbered in a "duplex-numeric" system involving both subject and geographical codes. The primary number is a general subject code in the range 5000-5999. The secondary number denotes a more specific sub-heading. The tertiary and lower numbers (if any) represent either a further subject breakdown or a specific geographical location, organization, or some other individual entity. Many of the blocks include long subseries documenting activities at particular foreign posts or nations; their subnumbers are usually assigned alphabetically by name of post city or country.
The 5000 block proper is divided into two parts for security reasons: the Unclassified files sub-sub-series (RG76-B-1-c-i) and the Classified files sub-sub-series (RG76-B-1-c-ii). The files or file parts containing material classified above "confidential", were segregated by the Department for separate storage. Different parts of the same file may be separated if some contain classified records and some do not. Thus researchers should check both sub-sub-series for all file parts of a given file.