Hi, John.
Could be fibreglass - many stack hats were from that in times gone by.

Just my 0.02.

could be bakealite. or pvc. modern ones are impact resistant abs

The one I have looks the same and my Euclid helmet that has not been painted on the inside shows that it is bakealite in my opinion.

To anyone who wants to see the helmet for themselves, our meuzeum Bouwmachinesvantoen in the Netherlands is open one Sunday in the month. But on special request for foreign guests who are on holiday, we make an exception.
So if you're in the area, let us know and we'll arrange a tour.

www.bouwmachinesvantoen.nl

Neighbor wore one that looked like the one in the first picture with the Caterpillar on it. After him wearing it 30 or 40 years it broken (without his head being in it). You could clearly see the fiber glass in it where it broke.

Hi, Ray54.
30 or 40 years???????????????????????????

Last time I checked DowNunda - which admittedly was a while ago now - there was a 3-year expiration date on the whole danged hat, dome, webbing, the lot.

PLANNED obsolescence.

Just my 0.02.

.Wonder what vintage, year, the fiber glass hat was made? Back in the early 60's our hard hats were made of Aluminum. It was a game to grab the hat by the brim and bang it on top of the hat your buddy was wearing. Still have my first AL hat.

yes and any damage at all must be replaced. discoloured or warped replace, scratched supposed to replace, certification label illegible replace it. paul, a retired truck and dog driver i know told me he was working on a main roads job before he retired, he had to wear a hard hat while inside the cab. if something is big enough to crush the cab the hard hat wont save you. get out the cab yes have it on but while sitting in the truck what a joke.

Hi, Folks.
If'n my mem'ry serves me right - which it still occasionally does - aluminium, or 'tin foil' hats were banned DowNunda back in, I think, the 1960s or 1970s 'coz a sharp object could pierce the hat and still 'gitchyer', maybe even turning a sharp corner of the hat into your head as well.

Just my 0;.02.