Actually, they look like this chaps:
But, uh, I'll take the gladiator style ones instead! (Like the solitary example in Betrayal.)
But isn't that the Mantilla-pattern (respirator)?
It's called a Sarum pattern respirator in Betrayal. If it's called Mantilla pattern somewhere else, I'm wasn't aware of it/forgotten it. :)
Horus Heresy Book One - Betrayal, according to lexicanum's page on power armour.