Above are two Russian portraits painted on wooden panels, with the distinctive “recess” creating a raised border seen in many icons. One is painted in the 16th century and the other in the early 17th century. Both contain similar stylized depictions of the subjects features, hair and foreheads. Both have inscriptions along the top (although the painting on the left’s inscription is faded) in Cyrillic.
However, only one of these paintings is an Icon. The other was never even intended to be thought of or used as a Holy Icon.