Professional Sports Authenticator (PSA) has initials that may show up on the label. Below are some of them: MK Marks OC Off-center OF Out of Focus PD Print Defect ST Stain "Qualifier In some cases, a card will be designated with a qualifier. A "qualified" card is a card that meets all the criteria for a particular grade, but fails the standard in one area. For example, a card which exhibits all the qualities of a NM-MT 8, but is 90/10 centered left to right, will receive a grade of NM-MT 8oc. The "OC" stands for off-center. Here is a brief list of qualifiers: OC (Off-center), ST (stain), PD (Print Defect), OF (Out of Focus), and MK (Marks). " PSA Resources - Qualifier