The Inscription on His Ring:

Hazrat ‘Amr bin ‘Uthmaan (rahimahullah) mentions that the ring of Hazrat ‘Uthmaan (radhiyallahu ‘anhu) had the following words inscribed on it, “I have brought Imaan in that Being who has created everything in its due proportion.” (Siyar A’laam min Nubalaa 2/156)

Demise:

Hazrat ‘Uthmaan (radhiyallahu ‘anhu) was approximately 82 years old when he was martyred. (Taareekh-ul-Islam 2/481)

He was martyred on Friday the twelfth of Zul-Hijjah in the year 35 AH (Siyar A’laam min Nubalaa 2/162)

Period of His Khilaafah

Hazrat Qataadah (rahimahullah) reports that the period of the khilaafah of Hazrat ‘Uthmaan (radhiyallahu ‘anhu) was twelve years. (Siyar A’laam min Nubalaa 2/161)