retroreflective sheet material is produced by forming sheet material with closely spaced retroreflective formations on one face and depositing on this face silver and copper atoms having high kinetic energy to provide a reflective metallic deposit comprising a base layer of metallic silver and an overlying layer of metallic copper . an organic protective coating is thereafter applied over the reflective metallic deposit . light rays passing through the front face of the body enter the retroreflective formations , impinge upon the interface provided by the silver base layer and are retroreflected therefrom . as a result , the sheet material exhibits a bright white appearance in daylight as well as a bright white coloration at night when an incandescent beam impinges thereon .