From the longer Wikipedia page 
Diplomatics (in American English, and in most anglophone countries), or Diplomatic (in British English), is a scholarly discipline centred on the textual analysis of documents – particularly, but not exclusively, historical documents. It focuses on the conventions, protocols and formulae that have been used by document creators, and uses these to increase understanding of the processes of document creation, of information transmission, and of the relationships between the facts which the documents purport to record and reality.
The discipline originally evolved as a tool for studying and determining the authenticity of the official charters and diplomas issued by royal and papal chanceries. It was subsequently appreciated that many of the same underlying principles could be applied to other types of official document and legal instrument, to non-official documents such as private letters, and, most recently, to the metadata of electronic records.
Diplomatics is one of the auxiliary sciences of history. It should not be confused (as it often is) with its sister-discipline of palaeography. In fact, its techniques have more in common with those of the literary disciplines of textual criticism and historical criticism.
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