Hi,
OK I have a question for you....What book are you reading??... as some of the ones out there are full of misinformation. Some are really awful...even the ones written by ladies who claim to be "experts".....NOT......and they do more harm than good. In an earlier thread I highly rcommended you purchase "Vintage Hats and Bonnets" by Susan Langley, both editions. Best one out there so far.
I agree with 1950's...later in the decade and it is possibly very early 1960s. The style looks more 60s 70s, but those little clampers date it earlier, as said.
It is made of what appears to be a synthetic straw or a natural straw that has been glazed/treated. Not HH.
B