This original bronze pendant dates back to the 9th-11th century AD. It is from the Byzantine Empire and inscriptions are written in ancient Greek.
The inscription on the front of the pendant is a portrait of a man wearing elaborate robes whose arms are outstretched in prayer. On either side of the man are two triangular motifs that may be depicting palm branches. Above the man, an inscription identifies this man as St. John the Theologian. St. John is also known as John the Beloved, John the Divine, John the Evangelist, or John the Revelator. He was the son of Zebedee and Christ’s beloved apostle. He wrote the Gospel of John, the first Epistle of John, and Revelation. The inscription reads ὁ θεολὸγοϛ (The Theologian, John).
On the back of the pendant, a similar figure is inscripted, with a Panaghia inscription above it. Panaghia, or All-Holy, is a title for Mary, the mother of Jesus used in Orthodox Christianity. Its inscription reads Παναγήα (All Holy, Virgin Mary) (Byzantine).
The cross has been a major part of Christianity ever since Jesus was crucified by the Romans. However, only after the Roman emperor Constantine converted to Christianity was it used as a symbol of the faith. It was originally worn by cardinals and others with high position in the Church, though now it is much more commonly worn. This pendant probably belonged to a clergyman as part of his religious attire (Symmons-Roberts).
“Byzantine Solid Bronze Pendant Cross: St. John and Panaghia.” Fragments of Time.
Symmons-Roberts, M. The Cross. Retrieved from http://www.bbc.co.uk/religion/religions/christianity/symbols/cross_1.shtml