This series consists of subject index cards which record correspondence received by the agency. The yellow cards are divided into five columns with headings giving the following information; Registration number, Number and Date of Letter, Date of Receipt, From whom received and Subject. The cards are divided using coloured tabs. It is not known whether the colour of the tabs is significant or not. Many of the entries refer to a 'C.G.'[Comptroller-General] annual single file number, which suggest this series may relate to accession series MP923/5 C.G. file movement registers and therefore provide a control system for CRSA425 and CRSB13. 'T&C' is also noted as a prefix to many of the file numbers. This refers to correspondence relating to the Department of Trade and Customs, which also suggests that series CRSA425 does relate to these cards.