Some writers think it depicts a kitchen slave character from a Greek comedy and certainly it looks like a theatre mask or a decoration inspired by one since there are no eyeholes.
So where is this from?
Ai Khanoum in Afghanistan!
There's currently a wonderful show on at the Art Gallery of NSW of Lost Treasures from Afghanistan which I havnt seen yet due to having a broken arm.
Ai Khanoum is thought to have been Alexandria on the Oxus mentioned by the geographers.
Here's a map. Sadly the site was been damaged by fighting between the Russians and Afghans since it was studied by French archaeologists but here's a map.
Finally a coin showing Eucratides. Thats probably a helmet even if it does like a lot like a flattened version of a pith hat although perhaps he just preferred hats to wreaths ?