A mold for imparting a marking including a requisite optical element to the outer surface of an article formed from a ductile material, said mold comprising: a marking surface for imparting the mark to an outer surface of the article by way of localized plastic deformation of the material from which the article is formed upon the mold and the article being urged against each other, said marking surface including a micro-structure formed by an arrangement of a plurality of micro meter sized recessed or protruded entities; said entities are arranged in a predetermined arrangement in relation to each other and said entities being arranged as a micro-structure having two and a half dimensions (2.5D), wherein said entities are arranged in an inverse arrangement in respect of the requisite optical element to be formed on the surface of an article, and said entities are arranged so as to provide one or more recesses extending in a direction of from said marking surface into the mold; wherein said one more recesses are sized and shaped such that upon the mold being urged against the article, the requisite optical element is imparted to the article upon deformation of the ductile material so as to conform with the surfaces of the plurality of micro meter sized recessed or protruded entities and wherein ductile material is plastically deformed and urged into said one or more recesses and conforms with the recesses, wherein deformation and flow of the ductile material into the recesses reduces lateral stresses imparted to the mold adjacent the recesses, and ductile material urged into the recesses forms a portion of the material from deformation of the ductile material which forms the optical element being imparted to the article by the entities with the requisite optical element having two and a half dimensions (2.5D); and characterised in that the recesses do not have any laterally extending undercuts such that the material which is urged into the recesses and which forms a shape defined by the geometry of the recesses is not damaged when the mold is removed from the article following formation of the marking. a marking surface for imparting the mark to an outer surface of the article by way of localized plastic deformation of the material from which the article is formed upon the mold and the article being urged against each other, said marking surface including a micro-structure formed by an arrangement of a plurality of micro meter sized recessed or protruded entities; said entities are arranged in a predetermined arrangement in relation to each other and said entities being arranged as a micro-structure having two and a half dimensions (2.5D), wherein said entities are arranged in an inverse arrangement in respect of the requisite optical element to be formed on the surface of an article, and said entities are arranged so as to provide one or more recesses extending in a direction of from said marking surface into the mold; wherein said one more recesses are sized and shaped such that upon the mold being urged against the article, the requisite optical element is imparted to the article upon deformation of the ductile material so as to conform with the surfaces of the plurality of micro meter sized recessed or protruded entities and wherein ductile material is plastically deformed and urged into said one or more recesses and conforms with the recesses, wherein deformation and flow of the ductile material into the recesses reduces lateral stresses imparted to the mold adjacent the recesses, and ductile material urged into the recesses forms a portion of the material from deformation of the ductile material which forms the optical element being imparted to the article by the entities with the requisite optical element having two and a half dimensions (2.5D); and characterised in that the recesses do not have any laterally extending undercuts such that the material which is urged into the recesses and which forms a shape defined by the geometry of the recesses is not damaged when the mold is removed from the article following formation of the marking.