Seals (bullae) from late 1st Temple period shed light on the bureaucracy & officials of ancient Jerusalem
The sealings (bullae- from which the Hebrew word for stamp, “bul”, is derived) are small pieces of clay which in ancient times served as seals for letters. A letter which arrived with its seal broken was a sign that the letter had been opened before reaching its destination. Although letters did not survive the horrible fire which consumed Jerusalem at its destruction, the seals, which were made of the abovementioned material that is similar to pottery, were actually well preserved thanks to the fire, and attest to the existence of the letters and their senders.
http://www.heritagedaily.com/2017/09/seals-bullae-late-1st-temple-period-shed-light-bureaucracy-officials-ancient-jerusalem/116392