The head is one of the best I have seen from you, but some of the lines are way too sharp.
Shading: Very well done makes the texture have a smooth feel to it.
Mapping: Polar coordinates am I correct? but anyway it is mapped pretty damn well which makes the plates look quite nice, but I don't know what the next plate will look like at the top since it might fold into the center.
Front could do with some more work, but the rest is clean and fine.
Rating for a wip 9/10 could do with some improvements, but it is a clean and well detailed wip.