Open oval shape first appeared around 500 BC in the Southeast Asian region where the Austronesian culture flourished e.g. in Taiwan , in the Philippines , and in the southern and central region of Vietnam .
The shape is endemic throughout the region of Southeast Asia .
Open oval shape first appeared around 500 BC in the Southeast Asia   region where the Austronesian culture flourished e.g. in Taiwan , in the Philippines , and in the southern and central region of Vietnam .
The shape is endemic throughout the region of Southeast Asia .