A RFID tag structure determining the authenticity of an article, and an information processing system for reading RFID tags, enable authenticity determinations of articles using read only RFID tags. A plurality of RFID tags, each holding tag information inside ROM (read-only memory) and responding to tag information via a radio wave received from a reader, are designed to have a service identifier which designates a common utilization goal for which the same value is set, and service data which sets different values for the respective RFID tags, as tag information. By dividing the data structure of a RFID tag having a read-only memory into a service identifier, which is common to a certain product, and sequential data for managing individual products, it is possible to confirm that an article is authentic by simply confirming the service identifier.