This egg was laid by a "golden comet" that I think is 2-3 years old - Hot Wings. The former owner fed cracked corn, no grit, and kept his chickens penned. She resumed laying around 2 weeks after being fed a proper layer pellet. She has not molted and is laying about 26-28 days out of every 30.
Egg was laid the day after Hot Wings failed to lay. This egg was followed by a soft shelled or shell-less egg that broke in the nest box. I can't 100% confirm it's the same chicken but I believe it was. I think this egg stayed in the "shell maker" too long, and the one behind it left a blank spot in the extra layer of calcium.