A covert label structure comprising a three dimensional diffracting optical element layer (100) having a depth profile for producing a predetermined pattern, wherein different portions of a top surface of the diffracting optical element layer (100) have at least two different depths relative to a bottom surface of the diffracting optical element layer (100), wherein the depth profile spans across two dimensions of the top surface of the diffracting optical element layer (100), and wherein the top surface reflects light according to the predefined pattern and an overcoat layer (108) over the top surface of the diffracting optical element layer (100) wherein the overcoat layer (108) is opaque to at least one wavelength of light.