Courtesy of National Museums Liverpool, World Museum
Amulet of the type known as a 'magical gem stone' which was used as a ring as it is obvious from the surface at the back of the ring and the little clasp part on one of its edges. The inscription is in Greek letters:
C T A
Y PE B
O H Θ
M H N
The inscription is an invocation for help from Christ to a person called Mina.