Tag inside helmet:
小田郡山田村中
Oda-gun, Yamadamura naka (location names: Oda county, Yamada village. This is in Okayama prefecture)
笠原重雄 Kasahara Shigeo (personal name. Kasahara/Kasawara is the family name, Shigeo is the first name)
This leads me to believe the symbol in the front of the helmet is the owners initials - SK - written stylisticly overlapping.
The other, very faint label, reads
昭和十九
Showa 19 (1944)