Your chipcard is supplied with an electronic seal. This procedure is called the NullPIN procedure. As with conventional seals, this seal does not prevent access to your card, but enables reliable control of the integrity of the card. If the NullPIN is no longer set, this is a sure sign that the card has already been used (possibly by a third party). Thus, a misdemeanor of this kind can be recognized reliably and queried by the card owner.