In a printing group which is intended for value marks printing (e.g. franking), a checking device is inserted in order to prevent misuse, i.e. not credited stamps, by manipulation of the current feed, or manual operation. This checking device counts every single printing operation, thanks to its on current supply. The meter reading of the checking device can be compared with the reading of the usual printing group meter. In case of a discrepancy between the two readings, the printing group jams or an alarm goes off, via the control electronics of the printing group, e.g. in the form of a security card. A great advantage of this checking device is its complete storing in the checking device itself of the printing operations and all manipulations or attempts at manipulation.