(Greek: diploma, an ancient writing; literally, paper twice folded)
The science of ancient official documents; it arose during the Middle Ages in the necessity for safeguarding from forgery papal Bulls and other instruments.
The procedure includes the study of the text of the document; manner of dating; signatures; attestations of witnesses; seals, and the attachment therof; the material and the manner of folding; and handwriting.
The cross, as a siguature or the equivalent thereof, has been always important, as are such details as the Tironian or shorthand notes.
Famous examples of spurious documents discovered by this means include the Forged Decretals and the Donation of Constantine.
The true science of diplomatics was defined by Jean Mabillon in his celebrated work, "" (1681).
New Catholic Dictionary