Signet Matrix; Seal Matrix; 1750-1800; Possibly made in Birmingham 1 Presented by Francis Buckley; 1934. A 'signet' or 'seal matrix' is a small stamp used for impressing the mark of its owner in wax onto documents. The majority of examples are finely made of moulded translucent glass; in this case translucent blue. Several bear engraved inscriptions in reverse; as in the case of this example. The word 'PRODIGIOUS' and design of a male figure with raised arms may have had some specific significance at the time.