Gold, Type I (99.7% gold minimum), Type II (99.0% gold minimum), Type III (99.9% gold minimum), Grade A (Knoop hardness 90 max), Grade B (Knoop hardness 91-129, incl.), Grade C (Knoop hardness 130-200, inlc.), Grade D (Knoop hardness 201 and over), Class 00 (0.00002″ minimum), Class 0 (0.00003″ Minimum), Class 1 (0.00005″ Minimum), Class 2 (0.00010″ Minimum), Class 3 (0.00020″ Minimum), Class 4 (0.00030″ Minimum), Class 5 (0.00050″ Minimum), Class (0.00150″ Minimum)