Definition of Signet- A seal or ring used by an a official much like a personal signature to give authority to a document.
Here are some biblical examples of usage:
Righteous Examples
Joseph received Pharaoh's ring because he interpreted his dream.The ring was placed to Joseph authority so he could rule over Egypt's well affairs. Genesis Chapter 41
Mordeci was given the ring from Ahasuerus after being proven a friend of the Persian Kingdom, and Esther set Mordecai over the house of Haman. Esther Chapter 8.
Zorobabel was like a signet ring because he won a contest using wisdom to remind King Darius of his promise to rebuild Jerusalem. 1 Esdras chapter 4, Sirach chapter 49:11.
Unrighteous Examples
Jezebel took the signet from her husband Ahab to bear false witness and murder Naboth stealing his garden which was coveted by her husband.
In conclusion, we can learn from the scriptures that a signet ring was utilized as proof of identity, receiving of goods, given to for show of loyalty, wisdom, and abused for ill-will as power of authority. The power of the signet ring lays in the hands of the beholder.