Throughout his career, Diamond kept a personal file of records in chronological order. Sometimes this file contained copies of the messages he sent, but at other times he included copies of incoming messages and copies of correspondence that had been sent to him by others. Occasionally, a speech draft or a copy of minutes or other records are in the file.

Although the records are found in one long chronological series, several distinct parts exist. The earliest file, dating from 1955 to 1958, contains primarily outgoing messages and personal items on finances, travel arrangements, and publications. It includes information on: EDI courses; Diamond's letters to Bank officials during his missions in Ethiopia, Greece, Turkey, and Tunisia; a letter to Newton Parker, March 24, 1958, on the roles of economic institutions in Honduras; and a memo to S.R. Cope of April 1, 1958, reporting on Davidson Sommers' meeting with a Yugoslav representative on future loans to Yugoslavia.

Records also relate to Diamond's work in India as an advisor to the Industrial Credit and Investment Corporation of India (ICICI). Beginning with his preparations for the assignment in 1958 and continuing into 1960 after Diamond returned to the Bank, the files provide an exceptional view of the early organization of the ICICI and the establishment of its policies. Included are: incoming and outgoing correspondence; notes of meetings; reports; and clippings; as well as purely personal correspondence. Correspondents include: Eugene Black andGeorge D. Woods; ICICI officials; Indian government officials and industrialists; the IBRD resident representatives in India and Pakistan; and various staff members in World Bank offices in Washington. Some correspondence discusses the establishment of the Pakistan Industrial Credit and Investment Corporation Limited and developments in Ethiopia.

The bulk of the series relates to Diamond's assignments at the Bank between 1962 and 1978, when he retired. For the first eight years the files contain primarily copies of Diamond's outgoing messages; thereafter the files increasingly include copies of incoming records, such as reports from the field and copies of records sent to him while he was on mission travel. The files from the IFC period contain many records about the development banks in South Asia and North Africa. When Diamond was a Director of country programs in the South Asia Regional Vice-Presidency, the files include records related to the Tarbela Dam project and the efforts to assist Bangladesh. The records in these files are largely duplicates of those in the official files of the Bank, but their chronological arrangement allows the user to see the variety of issues that Diamond was handling at the same time and to trace the evolution of his and the Bank's responses to events.

The final part of the series contains records relating to Diamond's work as a consultant to IFC between 1980 and 1990. The earliest records relate to IFC's role in the work of the Societe Internationale Financiere pour les Investissements et le Developpement en Afrique (SIFIDA), but the majority of the records relate to the Banco Portugues de Investimento SA (BPI). In 1978 a group of Portuguese industrialists created an Executive Group to develop a private financial institution to promote private economic development. They sought the involvement of the IFC, and the IFC engaged Diamond as its consultant on the BPI. The records related to this work includes both incoming and outgoing correspondence.