Diplomatic is the analysis of the protocols and forms of documents -- the formulae or protocol of documents. Its origins really lie in the late seventeenth century, its having developed out of disputes about the privileges of Benedictine Abbeys in France. As a consequence, Jean Mabillon (d. 1722) produced his De Re Diplomatica in 1680/1, analysing the constituent clauses of 'charters' in favour of the beneficiaries to assess their authenticity. His work was followed in France by Doms Toustain and Tassin, Nouveau Traité de Diplomatique (1750-65). Diplomatic developed in England at about the same time, principally through the work of Thomas Madox in the early 18th century, his principal work of diplomatic being Formulare Anglicanum (1702) and History and Antiquities of the Exchequer (1712), although he also published Firma Burgi (1726). Contemporaneously Thomas Rymer (with R. Sanderson) published his Foedera (1704-32). Diplomatic, as a method of assessing the authenticity of records, has largely been concentrated on the Anglo-Saxon diplomas ('charters') and on the private charters, particularly early grants to religious houses in the early 12th century. Absolute authenticity, however, is not not always significant, in the sense that, although some 'forged' documents may have been entirely fraudulent, others might have been simply 'intelligent' reconstructions of a past event which took place by oral disposition; although the charter may not be authentic it may represent what had happened, if with embellishment (such as impossible witnesses).
Another use of diplomatic is now the study of formularies as part of administrative and bureaucratic developments. This aspect is of considerable use for palaeography for it indicates the development of common form in documents -- the formulary and the formulaic -- which assists with understanding not only the development of the documents but, for practical palaeography, what form of words might be expected. For example, it is fairly clear that the Statute of Quia Emptores more consistently introduced into the private charter the formulary: de capitali(bus) domino (dominis) feodi ... faciendo inde servicia debita et consueta..., so that charters containing this clause, but without a date, may be inferred to be after 1290.