Abstract: The invention relates to work pieces (2), such as surgical instruments provided with a machine-readable data carrier (1). Said data support contains a data section (3) with individual cavities (4) arranged therein, forming a two-dimensional matrix code (5). The cavities exhibit a particular advantage in that they are machine-cut, especially by means of boring. Damage causing structural alterations to the material occurring when a code is burnt in by means of laser radiation can be reduced in a reliable manner. The contrast effect of the cavities is sufficient and the data support is particularly resistant to mechanical influences.