It was narrated from Anas that:

The Prophet ﷺ had a ring and he said: "We have had a ring made with an inscription, and no one else should copy this inscription." It is as if I can see its shining on the little finer of the Messenger of Allah ﷺ.

أَخْبَرَنَا عِمْرَانُ بْنُ مُوسَى، قَالَ حَدَّثَنَا عَبْدُ الْوَارِثِ، عَنْ عَبْدِ الْعَزِيزِ، عَنْ أَنَسٍ، أَنَّ النَّبِيَّ ﷺ اصْطَنَعَ خَاتَمًا فَقَالَ " إِنَّا قَدِ اتَّخَذْنَا خَاتَمًا وَنَقَشْنَا عَلَيْهِ نَقْشًا فَلاَ يَنْقُشْ عَلَيْهِ أَحَدٌ " . وَإِنِّي لأَرَى بَرِيقَهُ فِي خِنْصَرِ رَسُولِ اللَّهِ ﷺ .