During World War II, an American dog tag could indicate only one of three religions through the inclusion of one letter: "P" for Protestant, "C" for Catholic, or "H" for Jewish (from the word, "Hebrew"), or (according to at least one source) "NO" to indicate no religious preference. Army regulations (606-5) soon included X and Y in addition to P, C, and H: the X indicating any religion not included in the first three, and the Y indicating either no religion or a choice not to list religion.