Material confusions in the production process can have severe consequences for the later usage of steel products. Thus steel manufacturers strive for continuous and reliable material tracking. The automatic stamp-identification system in operation at Georgsmarienhütte features high fault detection rates for continuously cast ingots, reduces manual detection efforts and eliminates errors caused by manual fault detection techniques. Schematic diagram and user interface of this system are described. Lightness profiles transverse and alongside of the line of figures are compared. Vector field of the directions with the greatest lightness changing in the original picture are shown. The fault detection rate has averaged 95 % since the initial start-up of the system two years ago.