This is the standard US M1 helmet. It was generally worn without a helmet net, but , of course, photos exist with a net.
The band would differentiate between the various unit level of the parent company. Generally aWHITE band for regimental or company level and YELLOW for divisional units. Other colours for other units also exist.
There was no agreed method of applying the markings, the size of the lettering or the addition of specific unit markings. Any photo gallery may contain any number of variations on the theme!