To discriminate a bankbook by confirming identification information such as the number of bank accounts or the like from its cinders when the bankbook is burnt by an accident by a method wherein the identification information is provided with ink in which inorganic fluorescent pigment is dispersed at least on one position on a base material of a cover, a back cover or a back of the cover, etc., of the bankbook.

As an inorganic fluorescent material, colorless and transparenct or white one which changes color tone pattern by irradiation with ultraviolet rays, and has a refractive index same as or approximating to that of the vehicle resin when it is contained in vehicle resin is preferred. Concretely, zinc sulfide fluorescent material and yttrium florescent material are used. After the bankbook is burnt to ashes, a part of the bankbook which is burnt to ashes and on which fluorescent material is printed, is irradiated with ultraviolet light of a black lamp, the fluorescent material of a color tone pattern is excited to emit fluorescence in blue green color, the number of bank account is so seen as to float up, and can be confirmed. The inorganic fluorescent material does not undergo change of its structure at burning temperature of paper or the like. If ashes are not collapsed, they can be easily verified.