FIELD: marking of defective securities. SUBSTANCE: apparatus used for destroying imprints occurring on imprint medium during medium displacement has linear motor and correct marking detector. Mentioned linear motor has movable part with marker, Mentioned detector is mounted on linear motor in direction of imprint medium displacement. Detector functions to check for correct marking of defective imprints and its ability to be identified in the course of next processing of mentioned imprints. When particular imprint is considered defective by mentioned imprint quality control system, start-of-marking signal is sent to linear motor which operates in response to this signal and presses marker provided on its movable part to point of location of this imprint on its medium. Then end-of-marking signal is fed to mentioned motor and movable part of the latter is withdrawn together with its marker from imprint medium surface in response to this signal. EFFECT: facilitated procedure and reduced cost of marking defective securities. 9 cl, 3 dwg
