Bullard Model 4100. Interior tag reads: "Type 1 Class E, G & C" as well as noting that this protective headgear "meets Fed. Spec. GGG-H 142 & OSHA." It does have a severe crack in the left front brim (you can't really see it in the photo) so it probably no longer meets OSHA certification.
I don't know exactly how this ended up at my desk though it is not, as I'd first assumed, the "safety officer" hard hat my colleagues bestowed upon me years ago. That one sits under my desk next to a blaze orange safety vest waiting for the appropriate emergency. (You'll probably see that hat another day.)
Stylish? No. But if there's a hat to wear when the whole world is falling down around your ears, I'd go with this one.
PC 66: Leather Head
PC 52: Tschorn Meets Tricorne
PC 40: Loehmann's Lady's Lid