During the medieval period, seals were widely used in trading to ensure the authenticity and security of a document or letter. Bronze seals were a possession of the wealthy, since they cost more to produce than lead seals, and had a longer life span on account of the metal’s hardness. The social status of the owner was reflected in the size of the seal, with the combination of motif and text providing further insight into the owner’s identity, such as their place in a family.
Seal matrices were originally made of ivory or jet, but lead, bronze, and silver were the most popular choice of material from the 12th and 13th centuries onwards. They are usually circular, vesica-shaped, or shield-shaped, with a loop at the back.
To find out more about seals, please see: http://antiquities.co.uk/blog/uncategorised/seal-rings-intaglios-as-signatures/