Well Deas just between you and me , us dumb farmers don't pay much attention to OSHA.Even when it would be a good thing. The guy I am talking about knew how to pinch old Abe real hard before he let's the penny out of his fingers. His family was the majority owners of the rural telephone company, and as line man to general manager I suspect that is where he got the first hard hat. They sold out to Ma Bell in 59, so he was retired to farming before OSHA became thing.

Since the aluminum hat has been brought up, that is what he wore for a week or two after the demise of the fiber glass one. But he found another yellow one very much like the broken one. Don't know if it was a "real working hat" but kept him from sun damage on his ears with the bit of a brim.

As a tribute one of the neighbors talked a supply house out of the use of 6 yellow hard hats for the pallbearers to wear at his funeral. Those would of been OSHA approved.

In the Netherlands, they can create different sorts of things. I won't be surprised that it's made of some recycled organic garbage.

If the Caterpillar hard hat isn't metal and looks like plastic, it might be made from fiberglass, Bakelite, or even PVC. These materials were popular back in the day. Today, most are made from ABS plastic. I found a great guide on cleaning and maintaining different hat materials at matohash.com/blogs/news/cleaning-and-mai...ferent-hat-materials . It has some good tips for keeping old hats in good shape. But some tips work for helmets and protective gear, too.