im not sure but i think this is not a US tanker helmet there were other countries that used this style of helmet see pics below of a US WW2 tanker helmet.
I like it .
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have a look here Is this a real tanker helmet - U.S. Militaria Forum
Looking at it again, I agree with Nick.
Looks like an older football helmet... :P
That is because they were based upon a football helmet of the period.
Patton wanted them to be Gold in colour! worn with a green leather suit.
The helmet in question is actually a European made copy of the US "'38" helmet. These were produced post war for the US and other European countries that were equipped with US equipment since the US had stopped production of our version in '44 I believe it was. There was supposed to be a replacement, but it never came to light until much later with the adoption of the first "CVC".
These Euro cloned tanker helmets are easy to ID once you know what to look for. A couple quick ones, the ear flaps have the "X" straps on them, the dome is usually flatter, with a more squarish look to it for instance.
What is the value of such helmets?