The silver ring consists of a heavy, compact hoop ending in two stylized busts in relief.  In the centre of the bezel, in an incised circle, is engraved a cruciform monogram which can probably be read as the name Vlasios (ΒΛΑΣΙΟΣ).  The inverted inscription around the circumference of the circle reading +Ο ΜΕΛΑΧΡΗΝΟΣ (Melachrinos) is similarly engraved.  The name of the Melachrinos family is known from the 13th-14th centuries.  The ring probably belonged to a member of this family. 
A monogram in the shape of a cross on signet rings is an invention of the 6th century.   When rings have inverted inscriptions (i.e. in "mirror-writing") it means that they were used as seals, as the inscription could be read normally on the seal.  Thus the user of such a ring must have been some sort of official, who sealed documents and so on with his name.