A combination magnetic tag (10) is described comprising an optical part (20) and a magnetic part (30), the optical part including a plurality of optical elements for conveying an optical code and the magnetic part including a plurality of magnetic elements for conveying a magnetic code, the optical and magnetic codes being mutually complementary for verifying authenticity of the tag (10). Incorporation of both optical and magnetic codes into the tag is of advantage in that they are capable of rendering the tag less susceptible to copying. The tag (10) is relevant to appropriate to anti-counterfeiting applications.