Class D
From Thelemapedia
Within the official publications of A.'.A.'. and O.T.O., Class D documents are those that consist "of the Official Rituals and Instructions." (see Liber CCVII: A Syllabus of the Official Instructions of the A.'.A.'.)
Some examples of this class include Liber V (Reguli), Liber XXV (The Star Ruby), and Liber DCCC (Samekh).