Nice helmet, I would agree with most posts here on the chin straps, I would think that if somebody was trying to fake them, they would do a better job, so I would not change them either.
According to this extremely good reference web site, the triangle stamp is generic 'Army', Osaka is crossed cannons.
.: World War Helmets - Casque Type 90 :.
Great info, Steve-san. Thank you.
Mabe I should start learning French, I can only guess some of the words.
If you right click, do you get the option to 'Translate'