Usually a ring with a seal carefully crafted upon it that an important or rich person used to authenticate a document. It was used much like a signature on a document today. The ring of kings would carry the highest authority in a land and empowered subordinates to act for the king. Examples of such rings in the Bible are: Pharaoh’s ring given to Joseph (Gen 41:42); Ahasuerus’s ring given to Haman and then to Mordecai after Haman was hanged (Esther 3:10,12; 8:2); King Darius’s sealing the den of lions after Daniel was thrown into it (Dan 6:17).