A reversibly metachromatic toy having a platelike resin foamed substrate, a resin layer provided on both the outer side surfaces of the foamed substrate, and a reversibly metachromatic layer provided on at least one-side resin layer partly or all over the surface. The tape head may include a write element. Each tag comprises: a plurality of data symbols, including a plurality of first data symbols; a plurality of data elements; and one or more flags.