Chris, I just registered to this Site and this is my first reply. Re: the type 90 (on the right) note the shallow brim all around the circumference . It has the classic shape of the IJA (Army) and IJN (Navy) helmet. The larger helmet on the left in the photo is most probably designed for and worn by Civil organizations such as Firemen, Air Raid wardens IOW non-combatants. I don't presume to be an expert in Japanese helmets but I am seriously involved in studying about them so as to make up a display with a " head mannequin", helmet and liner, chinstrap, cover and netting. TEDJR