Sunan an-Nasa'i, Book 48, Hadith 241 (In-Book) ⓘ
It was narrated that Anas said: "The ring of the Prophet [SAW] was of silver, and its stone (Fass) was made of silver too."
أَخْبَرَنَا الْقَاسِمُ بْنُ زَكَرِيَّا، قَالَ حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنِ الْحَسَنِ، - وَهُوَ ابْنُ صَالِحٍ - عَنْ عَاصِمٍ، عَنْ حُمَيْدٍ، عَنْ أَنَسٍ، قَالَ كَانَ خَاتَمُ النَّبِيِّ صلى الله عليه وسلم مِنْ فِضَّةٍ وَفَصُّهُ مِنْهُ .
also referenced under: Hadith 5280 (Reference) & Volume 6, Book 48, Hadith 5282 (DarusSalam)