The faces are 10 degrees (i had to go measure, i'm not strange enough to know that kinda thing off the top) Which is fine as long as you keep your wrist low, if i made it again i'd go for something shallower and maybe slightly crowned, but then again this is not a mallet for delicate work.
I like the idea of 'Thor Mallets' everywhere to be carved, either that or inlayed with brass/copper/etc.