An identifiable mark on a portion of a polished facet of a surface of an article and being identifiable by an optical magnifying viewing device, the identifiable mark comprising a nano-structure formed by a two-dimensional or a three-dimensional lattice of a plurality of discrete nanometer sized recessed or protruded entities, wherein the entities are arranged within a predefined region of the polished facet in a predetermined arrangement in relation to each other. The predetermined arrangement of the entities is non-uniform and non-periodic arrangement, and wherein the entities are sized and shaped so as to cause optical scattering upon reflection of incident light having one or more predetermined wavelengths by the lattice at a predetermined angle of incidence to the lattice and the distance from the inner interface surface to the outer interface surface is greater than the amplitude of the non-marked portion of the polished face.