'Signet' in the Bible

Then the king removed his signet ring from his hand [that is, the special ring which was used to seal his letters] and gave it to Haman, the son of Hammedatha the Agagite, the enemy of the Jews.

Then the king’s scribes (secretaries) were summoned on the thirteenth day of the first month, and it was written just as Haman commanded to the king’s satraps (chief rulers), and to the governors who were over each province and to the officials of each people, each province according to its script (writing), each people according to their own language; being written in the name of King Ahasuerus and sealed with the king’s signet ring.

The king took off his signet ring which he had taken away from Haman, and gave it to Mordecai. And Esther put Mordecai in charge of the house of Haman.

Also, concerning the Jews, write as you see fit, in the king’s name, and seal it with the king’s signet ring—for a decree which is written in the king’s name and sealed with the king’s signet ring may not be revoked.”