It was narrated from Anas that:

The Prophet (ﷺ) [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 صلى الله عليه وسلم اصْطَنَعَ خَاتَمًا فَقَالَ ‏

‏ إِنَّا قَدِ اتَّخَذْنَا خَاتَمًا وَنَقَشْنَا عَلَيْهِ نَقْشًا فَلاَ يَنْقُشْ عَلَيْهِ أَحَدٌ ‏

‏ ‏.‏ وَإِنِّي لأَرَى بَرِيقَهُ فِي خِنْصَرِ رَسُولِ اللَّهِ صلى الله عليه وسلم ‏.‏