A large number of magnetic polymer elements are distributed at random in a base material of a object to be checked. Each magnetic polymer element includes an element main body formed of a high-molecular material, such as an acrylic resin, and magnetic metal powder contained therein. The base material is formed mainly of paper, and the magnetic polymer elements are incorporated together with wood pulp fibers in the base material. The elements and the fibers are tangled with one another in three dimensions. Indication data including figures, symbols, etc., such as post position numbers and bet numbers on betting tickets for publicly-managed gambling, are printed on the object. The indication data, along with a proper output signal obtained in accordance with the state of distribution of the magnetic polymer elements, are enciphered according to specific rules for enciphering, and are recorded in a code indicator section by means of a recording medium, such as a magnetic stripe which is magnetically readable or a bar code which is optically readable.