This armored mask featured very small eye slits, a cut away to get a cheek weld on a rifle, and a bend at the bottom to prevent spalling from striking it's wearer.
Big red arrows and circles pointing out the bit you're supposed to see through:
Typo, I just fixed it. I meant 'cheek weld'. But a cheek weld is when a shooter places his/her face on the stock of a rifle/shotgun to gain a more stable sight picture, which contributes to better accuracy.