1. An object identification system comprising: at least one memory; at least one processor configured to implement: an acquiring unit that acquires a captured image of each of a plurality of objects respectively having peculiar patterns on surfaces thereof, predetermined images being formed on the surfaces; a classifying unit that classifies, for each of the plurality of objects, the object into one of a plurality of classifications according to a deviation of a position where the predetermined image is formed with respect to a reference position of the object or a pattern of noise included in the predetermined image formed on the object in the captured image acquired by the acquiring unit concerning the object; a registering unit that registers, in the at least one memory, for each of the plurality of objects, identification information of the object, a pattern image indicating the pattern on the surface of the object, and a classification of the object in association with one another; a classification acquiring unit that acquires candidates of classifications, from anion the plurality of classifications, for a target object, which is one of the plurality of objects, on the basis of a result obtained by the classifying unit classifying the target object on the basis of a target object captured image obtained by capturing an image of the target object; a pattern-image acquiring unit that acquires, from the at least one memory, pattern images registered by the registering unit in association with the candidates of classifications acquired by the classification acquiring unit; and a specifying unit that specifies, as identification information of the target object, identification information associated with a pattern image matching the target object captured image from among the pattern images acquired by the pattern-image acquiring unit.