Unfortunately I see that time & time again in a certain era of homes around here... I've come across the glowing recepts one time, A homeowner called & wanted to know why the outlets in her dining room didn't "glow" anymore.. At first, I thought she had some hospital grade recepts with the neon lights in the face, but when I got there, the faces of her receptacles were simply ash... They disintegrated just taking the face plates off... These were original outlets from when her home was built.. (1969 I think) & there was no marking for copper only at that time... scary stuff!
The receptacle in your picture looks like a Rodale, it might've been original also!