Narrated Anas bin Malik:
When the Prophet (ﷺ) intended to write to the Byzantines, it was said to him, "Those people do not read your letter unless it is stamped." So the Prophet (ﷺ) took a silver ring and got 'Muhammad, the Apostle of Allah' engraved on it .... as if I am now looking at its glitter in his hand.
Narrated Anas bin Malik:
Once the Prophet (ﷺ) wrote a letter or had an idea of writing a letter. The Prophet (ﷺ) was told that they (rulers) would not read letters unless they were sealed. So the Prophet (ﷺ) got a silver ring made with "Muhammad Allah's Messenger" engraved on it. As if I were just observing its white glitter in the hand of the Prophet.
Anas b. Malik reported that Allah's Messenger (ﷺ) had made for him a silver ring. and got engraved on it (Muhammad, Messenger of Allah) and said to the people I have got made a ring of silver and engraved in it (these words) (Muhammad, Messenger of Allah). So none should engrave these (words) like this engravement.