Hans von Hammer
Well, I gave that some thought, and while I don't wanna exclude anyone, I can't put everyone in it either. Their were three distinct Allied helmet types, the American M-1 "Steel Pot", the classic "Tommy" helmet used by the Brits and British Commonwealth units, and the Brit Paras had their own helmet too...
Actually, the Brits had three (or techincally four) helment types for Normandy:
The classic Mk II
The new Mk III "turtle style" which was first used by some of the British assault troops
The Para's helmet
and its' close cousin, the Tankers Helmet, also introduced into combat in Normandy