This series comprises the 'official' papers found in Prime Minister (Harold Edward Holt)'s briefcase at the time of his disappearance from Cheviot Beach, near Portsea in Victoria, on Sunday, 17 December 1967. The value of the papers lies primarily in the fact that they happened to be in the briefcase at that particular time. Some of the papers relate to political matters current between Holt and other persons. They include correspondence concerning the relationship between William McMahon and John McEwen, Morris West and the Liberal Reform Group, the Australian Bankers' Development Refinance Corporation, C R Chapman and the Basic Industries Group.

The papers were kept by Holt's Principal Private Secretary until late December 1967, when they were passed to the then Secretary to the Prime Minister's Department (Sir John Bunting). They remained with Bunting's personal papers until 7 February 1975, after which they continued to be held in the Department of Prime Minister and Cabinet until transferred to archival custody in October 1987. The exception is a letter dated 9 December 1967, addressed to Holt by the Governor General (Lord Casey), which was returned to the Governor General’s Office after Holt’s death and is now in the Casey Papers held by the National Library of Australia.

The briefcase, and other personal items found in it, were retained by the Holt family until May 2002 when they were also transferred to archival custody (M4298).

Related series are M4297, M4299, M4300, M1945, M4962, M4963 and M4964.