Where did the Prophet wear his ring, what did it look like, and what was it made of? Did the Prophet wear a gold ring or anything made of gold before its prohibition? Is wearing a silver ring a Sunnah or merely permissible?

The Prophet, peace and blessings be upon him, used to wear his ring on the little finger of his left hand, and sometimes on his right. It was usually made of silver, and sometimes had a carnation agate stone. He would orient the stone towards the palm of his hand. He forbade wearing rings on the middle finger and the one next to it. He cast off his gold ring and prohibited wearing it. Wearing a ring is a Sunnah, and the Sunnah is achieved by wearing it even occasionally, but it is preferable to wear it continuously.