I use POO with my existing 00-99 number systems. Each suit is assigned a number: Clubs = 3, diamonds =4, spade = 5, and heart = 7. You can assign any number you wish. For number cards, the suit is combined with the number. Example: 5 of clubs = 53. 8 of diamonds = 87.
For face cards I assign a number of 6 to Jacks, 8 to Queens, and 9 to Kings. For face cards I have to reverse the way I read the numbers, so Jack of Spades = 56, or King of Clubs is 39.