A great seal is a seal used by a head of state, or someone authorised to do so on their behalf, to confirm formal documents, such as laws, treaties, appointments and letters of dispatch.
It was and is used as a guarantee of the authenticity of the most important and solemn records and documents.
This keeper may be a separate office but was also usually combined with that of the chancellor.
Great seals of republics usually show the nation's coat of arms (e.g. the Great Seal of the United States) or an allegorical image (e.g. France).
In monarchies, by contrast, the great seal is often changed some time after the accession of a new monarch as the seal often depicts the reigning monarch in full form.