PIVS XII PONT MAXIMVS & St. Christopher Medal

This item is for some type of medal. On one side is a pope, with the letters PIVS XII PONT MAXIMVS written on it, and on the other side is a St. Christopher medal. This looks as if it was on a FOB chain, or maybe was worn as a pendant. I'm not sure what material this is made of. Please ask questions before bidding.