The inside circumference measures about 21", which makes this a small hat - most likely for a petite woman or a teenage girl.  A circumference of 21" corresponds to hat sizes between 6-1/2 and 6-3/4 (U.S.).  Note that this a VINTAGE hat where the leather has hardened somewhat;  therefore it has less "give" than a new hat with soft, supple leather that stretches.

The top has an embossed "sunburst" pattern (see photo).  The band is a hardened three-strand leather lanyard with a gold-colored metal chain wrapped over and under it.  There is a gold-colored pin/medallion on the front of the chain;  this medallion is signed 'MONET ©'. on the back.  The medallion and chain are oxidized, similar to the aging of the hatband.  It looks to me that all this has been together for many years.  

Based on its appearance, I jokingly asked the woman where I purchased this if she had worn this to Woodstock in 1969.  The woman, who was probably in her 40s (I know better than to ask) looked at me seriously and replied that actually the hat had been her aunt's and that "Knowing her - maybe".  So essentially, I know nothing for certain, as usual...  

The Estate Sale was near Saratoga NY.  Woodstock was only a few hours south of Saratoga.