Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

I have a question about the shape of Hargis' motorcycle helmet on the left. First notice the shape of Cheney's on the right. Notice that it looks perfectly round. But, what about the other? Doesn't it look weird? Why is it flat on top? 

I know it has a thumbprint over it, a thumbprint which could not possibly have left a white mark unless the person doing it had something white and messy on his thumb. But right now, just look at the shape of the helmet. Any ideas about what is going on there? 

Let's hone in: