The 1955-59 Chevrolet and GMC originally came with a non-metal shield to direct light into the ignition switch to the key slot. This shield is almost always missing after fifty years. Most shrink after twenty years and fall from the switch. The accompanying photos show this snap-in shield in place. Even the die cast opening is notched on all switches to hold this non-metal plate. The illumination from the snap-in light bulb socket directs the illumination through the small lower opening, then to a hole in the switch, and finally to the key slot in the ignition cylinder. When the driver enters a 1955-1959 GM truck at night, he pulls the headlight switch and the illuminated key slot shows where to place the key.