Narrated Anas bin Malik:
Once the Prophet wrote a letter or had an idea of writing a letter. The Prophet was told that they (rulers) would not read letters unless they were sealed. So the Prophet got a silver ring made with “Muhammad Allah’s Apostle” engraved on it. As if I were just observing its white glitter in the hand of the Prophet (SAW).
Prophet (SAW) got a white silver ring made which glittered. Follow the Sunnah, get a silver ring made! ;)
It can be of any type: shiny, engraved, hammered, with or without stones.. Whatever you like! :)