Prime Rib can be graded as “Prime,” “Choice,” or “Select.” (Don’t be confused by the Prime in Prime Rib - that refers to the section of the animal, not the grade of the meat!) The main differences between Prime and Choice grading are Aging of the animal Marbling content Prime is the highest grade coming from the youngest animals and having the highest intramuscular fat marbling. The choice is the middle option. Select is the last!