Can definitely see that the 'armour' is contiguous and runs around the whole of the 'M1'.
Also can see that the right hand shoulder patch is the same style as those worn by Rebel troopers on Hoth - sorry the last is an observation not meant to derail the helmet focus.
Yeah I think those patches must be a Rank Identification of sorts. One more question to everyone: Are we sure that box on the strap on the poster helmet is an E-11 clip? It looks to straight to be a cut down sterling magazine