You get the price and the quantity and variety of food that is stated on your card.
A Standard All You Can Restaurant that works differently for each patron depending on the card they present.
Card One or Cardless: Just like any all you can eat place as many trips and drinks as you desire. And
a big price.
Card Two: Pay by the weight so much per ounce. A waiter may make up and bring the plate to you. Or you choose and take it to a weigh station. A target based on your sex, weight, and activity level might be suggested.
Card Three: Only vegan items allowed. No Meat as they define it.
Card Four: Only Adkins style plate allowed
Card Five: Various Religious, like Kosher, restrictions
Card Six: A diet based on your doctor's, your dietitian's, or Aunt Maude's advice.
Card Seven: Latest diet fads
Card Eight: Test Kitchen makes up plate, and you have to stay after school and fill out a survey form on the items you ate. Reduced fee or next time coupon.
Card Nine: The homeless plate The kitchen's mistakes, burns, overstocks etc. at a cheap or free price. Likely to go and from the side door in a stained paper bag
Cards Ten through Twenty: As market demands.
Maybe an Only CARBS card for those wanting to eat at home and just go out for dessert.
The use of a card operated gate(s) might be needed to keep people from scamming the system.