As an Alaskan, I have always held particular fascination with the battle of Attu and the Aleutian campaign.
Here are two helmets souvenir-ed from that battle.
First up is a rare small sized variant. The words "Attu 43 Japanese" are penciled inside the shell, hidden under the leather.
Blood stains are also evident. Very few prisoners were taken in this battle, and the vast majority of the 3000 man garrison died in battle or committed suicide.
There are very few of these helmets with Attu provenance around. There is a display case at the University of Alaska museum that features a helmet, but I doubt it is from Attu. Since they also display a German bayonet from the Aleutian campaign!
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Here is the second one, in a large size. I added the star. It is also a battle damaged helmet.