Janus, the personification of thresholds, beginnings, and endings, has had many depictions over the centuries. Common to them all and distinguishing him from every other occupant in the pantheon of Roman deities were his two faces opposite each other on either side of his head. He looked both ways with his two faces, and this, the Romans thought, made him the perfect god to preside over the boundary between any two given situations: war and peace, earth and heaven, past and future. He was the doorkeeper, the boundary master.

One conspicuous difference you’ll notice among Janus’ many depictions is that in some, his two faces are identical, and his head a perfectly symmetrical mirror image; while in others, his two faces are markedly different, one side bearded while the other side is not, or one side visibly aged while the other side is youthful.