Well waaay up here in Canada I've never seen a ridged egg like that in 50 plus years- mind you our winters are warmer then minnestotas'....lol. Could it be the hen has a blockage in the tube where the shell is added and hardened and the indents and ridges are from the muscles trying to push it out past that? There are some eggs that have sworls or roses on the ends, or bits and bumps of extra calcium, but those are unique! Thank you for sharing the pictures.
BTW I never knew until last year that some brown eggs, like the marans, have the color sprayed on at the very end just before it's laid and that's why you can wash the color off....
Could you maybe call a university and ask an ag prof what they know about egg formation?
Kelidei, the chicks will "moult" about 3 times between the chick and pol stage, but it isn't really called moulting until after their first winter and laying cycle. That's when they shed their feathers and stop laying for a while.