There are two types of marks on a bolt: The first is the manufacturer’s or importer’s mark, which is a symbol identifying the manufacturer, and The second is the grade mark (like: A2, A2-70,A2-80, A2-50, A4-70, A4-80, A4, B8M, B8, B7M, B7, 8.8, 10.9, 12.9, F593C, F593D, F593G, F593H,CL1- B8, B8M,F594C, F594D, F594G, F594H, A2-035, A4-040, F837B, F837C, F837E, F837) which is a standardized mark that identifies the material properties that the fastener meets.