Abstract: A sandwich structure is formed by a base layer and a protective layer that are assembled together through the interposition of a spacer layer therebetween, in such a manner as to form a tightly sealed, insulated hollow space, in which high-luminosity LEDs are arranged to illuminate the number plate through transparent portions of the protective layer. The LEDs are adapted to be connected to a power supply through conductive paths provided on the inner surface of the base layer.