Information is written onto the surface of an object using both an optically identifiable pattern and subregions that exhibit differing magnetic properties. The optically identifiable pattern is printed onto a printed region on the surface of the object using a printing medium that contains magnetic particles. The printed region includes both a first subregion that exhibits a first prevailing magnetization direction and a second subregion that exhibits a second prevailing magnetization direction. The first magnetization direction differs from the second magnetization direction. The first and second magnetization directions are imparted to the first and second subregions by magnetic fields being applied to the magnetic particles. An edge between the first subregion and the second subregion does not coincide with any boundary of the optically identifiable pattern. The printed region contains both optically encoded information and magnetically encoded information. Additional information is decoded using both the optically and magnetically encoded information.