This series consists of a cloth-covered booklet of registration sheets  for circulars and circular letters relating to medical topics covered in the correspondence series B539 kept by the Department of Defence's central registry. The booklet has a grey cover with 'Index' handwritten in red in the left corner, and "Circulars and circular letters Index" in pencil along the top. The inside back cover, has some illegible writing in red, and "circulars and circularletters 1917" written on it. The body of the sheet is divided into columns as follows :
 "No." : This column was used to give the circular or circular letter number"Prior" : Not used
"Subsequent" : Not used
"Date Registered" : The date on which the circular or circular letter  was registered
"From Whom" : This column was used to give the details of the sender  and the date of the letter
"Nature of Communication" : A summary of content
"Referred to" : The file number (from CRS B539) to which the circular  was attached
"Action" : not used.
 The last entry for 27 July 1917 (Cable number 53233) concludes this series.