I was cleaning a little the latest helmet iv gotten an m40 ,and left it by the window for minutes.It being a hot day the shell was very hot and it reminded me of the discomfort in combat when the weather was hot and the soldier had to wear the helmet.Their heads must have sweated a lot.I know when things where quiet they wore their soft caps.Another thing about this helmet is that one of the m40 vents looks like it was bunged up deliberately,to probably keep out the cold.in cleaning it ,a lot of the white wash is now showing,was this a standard thing the soildiers did with the m35s ect?lv