Tail light/brake light

In the later years with a plastic housing, they had a copper ring around the hole where the bulb holder went through. It had a separate ground wire that went into the harness. Those were famous for corrosion and bad grounds. The metal housing weren't as bad, but, still got corroded.....usually where the bulb made contact in the socket. I used to bead blast those sockets, blow them out, then spray them with lithium grease, install a bad bulb just to repaint the housing with some chrome spray paint, put in a new bulb, and then put it all back together again.