Rings of Kings used for Sealing Decrees
Source: TTT
Esther 3:12
On the thirteenth day of the first month, the royal scribes were summoned and the order was written exactly as Haman commanded the royal satraps, the governors of each province, and the officials of each people, in the script of each province and the language of every people. It was written in the name of King Xerxes and sealed with the royal signet ring.
Esther 8:8, 10
Now you may write in the king’s name as you please regarding the Jews, and seal it with the royal signet ring. For a decree that is written in the name of the king and sealed with the royal signet ring cannot be revoked.” / Mordecai wrote in the name of King Xerxes and sealed it with the royal signet ring. He sent the documents by mounted couriers riding on swift horses bred from the royal mares.