A double-layer system includes a metal layer facing away from a viewer and a coating facing the viewer. In order to make the layer system production process as simple as possible and to provide a sputter deposition method that dispenses entirely with the use of reactive gases in the sputtering atmosphere or requires only a small amount thereof, the coating is in the form of an optically partially absorbing layer which has an absorption coefficient kappa of less than 0.7 at a wavelength of 550 nm and a thickness ranging from 30 to 55 nm.