Double egg shell

Double egg shell

I’ve never seen this before, but I guess it occurs occasionally. This egg has two shells. There was a hen in the nest box, but it was probably laid by a hen before her. We have six boxes, but usually all the eggs (about a dozen now) are in just two boxes. This one looked just like this when I removed it. I’m not sure why the outer shell was half gone or why they are such a different color. That kind of suggests that the brown color is something that happens only shortly before the egg is laid.