First- sorry for the frozen chick.. the good news is that it was your last frozen chick.That is a silver Leghorn, the pattern is known as Silver Duckwing and many breeds have it.
Thank you for the Duckwing.. I read and read and all I understood was it is a colour pattern of the wing. I didn't understand which breeds have it and I didn't understand how is it related to the pattern of the back? Duckwing- this is color pattern, not shape, right? All silver duckwing patterns have the same stripey back?