Sunan Abi Dawud Book 36, Hadith 3
The signet-ring of the Prophet (ﷺ) was of silver with an Abyssinian stone.
It remained in his hand until he died, in the hand of 'Abu Bakr until he died, in the hand of 'Umar until he died, and in the hand of 'Uthman. When he was near a well, it fell down in it. He ordered to take it out, but it could not be found.
The signet-ring of the Prophet (ﷺ) was all of silver as was also its stone.