The portrait can be related to Philip I (the Arab). 

Marcus Julius Philippus (c. 204 – 249 AD), also known commonly by his nickname Philip the Arab, also known as Philip, was Roman Emperor from 244 to 249. He was born in Arabia Petraea, the Roman province of Arabia, in a city situated in modern-day Syria. He went on to become a major figure in the Roman Empire. He achieved power after the death of Gordian III, quickly negotiating peace with the Sassanid Empire. During his reign, Rome celebrated its millennium.

Among early Christian writers, Philip had the reputation of being sympathetic to the Christian faith. Probably for this reason it was even claimed by some that he had converted to Christianity, which would have made him the first Christian emperor. He supposedly tried to celebrate Easter with Christians in Antioch, but the bishop Saint Babylas made him stand with the penitents. Philip and his wife received letters from Origen.

Philip was overthrown and killed following a rebellion led by his successor Decius.