It is actually a Latin Phrase...
In whole it reads:
"In hoc signo vinces".
It is a motto meaning "In this sign you will conquer." And is the motto of the Knights Templar, top of the York Rite of...
Freely translated as With this sign you will conquer (lit. In this sign you will conquer), the words that an angel told the Roman Emperor Constantine, this saying refers to the uniform of the...