Data processing device, cash processing terminal, and data processing system

A data processing system, comprising:

• a cash processing terminal included in a cash processing terminal cluster in a local network, and including a data notification section that provides notification of serial numbers obtained by reading banknotes;
• and
• a data processing device provided between the cash processing terminal and an external network outside the local network, wherein the data processing device includes:
• a data acquisition section that acquires, in the local network, the serial numbers of which notification has been provided by the cash processing terminal,
• a storage controller that stores the serial numbers in a storage section;
• a condition acquisition section that acquires conditions of a decommissioned note serial number;
• and
• a serial number notification section that acquires a serial number satisfying the conditions from the storage section, and provides notification of the serial number to any cash processing terminal included in the cash processing terminal cluster, or to a cash processing terminal in a local network that is different from the local network.