Hi,
Hmmmmm. Can't seem to nail this one 100%. It is made of a fine quality sisal straw or buntal straw, which is/was used in better, higher priced hats. Although the style is more 1930's, the Sylvia label looks post WWII. The style is so very classic, it had a few revivals over the years. For now I am going with very late 1940s to mid 1950s.
B