Hazrat Ibn Umar radiallahu anhu says that Rasulullah sallallahu alayhe wasallam had a ring made of silver. He used it as a seal (Stamp) on letters etc., but did not wear it (JA)
English reference (JA): Book 11, Hadith 83 (JA)
Arabic reference (JA): Book 12, Hadith 88 (JA)