Cartwheel is the spoke effect you get from light coming off the surface of a coin...when you tilt it side to side... most noticeable with larger coins, like Morgans.
Okay,going look at some see if can see this on them ..... probably don't have any that grade 65 or 66.....................but thanks FISHY
Doesn't have to be a grade that high...I am holding a MS63 Walker right now that has a nice cartwheel.