Hippie Boho costume retro shirt VINTAGE

This is a small size shirt that fits a petite adult woman with small bust or a teenager. The fabric is shiny, maybe polyester? The label says "ILGWU" "union made" "ladies garment workers union" and other things I can't make up (see photo). Two slits on the sides and 3 buttons at the neck area with loops that go around the buttons. Sorry I am not yet familiar with the correct seamstress lingo. It's in good condition!