Abstract: The invention relates to marking of industrial products or individual parts thereof by burnt-in alphanumeric symbols and/or company symbols. To be able to apply in a space-saving and cost effective way a machine-readable, informationally identical additional coding, this additional coding is applied, integrated in the symbol, in such a way that distinctly deeper burnt-in locations, which are in themselves machine-detectable, are arranged along the trace of each and every symbol at several predetermined places distributed in a manner individual to the symbol. The deeper burnt-in locations may take the form of a blind hole, for example in the case of cast workpieces, or of a through-hole, for example in the case of sheet metal components. The additional coding can be applied in the same operation as the basic marking without noticeable time loss and without requiring additional space.