There are 2 different answers, both of them correct:
Jesus Savior of Mankind
Iesus Hominum Salvator
(classical Latin does not have a J)
In Hoc Signo [Vincet]
The words heard by Constantine on the eve of a battle. He saw the cross in the heavens and heard “in this sign conqueor” and that was the beginning of his conversion to Catholicism.
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