1. Method of classifying a steel specimen, comprising: presenting a steel specimen to a coil means, said coil means receiving an excitation current and producing an electrical output dependent on an induction value of said specimen; applying an excitation current to said coil means at each of a plurality of excitation frequencies in series and determining a respective induction value of said specimen at each of these frequencies; deriving for each of a plurality of possible steel grades a separate determinant function, said separate determinant function being a sum of a series of products of attributes of said specimen comprising said induction values and predetermined weighted coefficients reflecting the degree to which the respective attributes are effective to discriminate that possible steel grade from the others; producing a series of differing discriminant functions correlative with the differing possible steel grades and comprised of differing sets of weighted coefficients applied to the same values of said attributes of said specimens; and determining which of the differing discriminate functions has a maximum numerical value as a measure of which of the known grades most closely matches that of the specimen.