If that was my calf I would call Dr. U and send him a pic and find out if he has ever seen anything like it before, if he had no idea I guarantee he would drop by to take a look when he is in the area..
That is very odd and you will get diddly for it if you are planning to sell it with that visible, call your vet and see what they think (it is usually a free call)..
Keep us posted if and when you find out,,very odd indeed.. :?