Suzy Perette Audrey Hepburn Black Dress

Vtg 50s Suzy Perette Button Accent  Black Cocktail. Suzy Perette New York Zipper gets stuck almost to top. I don't want to force it. On the neckline there is loose thread and the area may have to be ironed down so it doesn't lift.  I think this dress is polyester but I'm not sure. There is no size indicated. Measurements Chest 18" Sleeve 6" Waist 16 1/2" Hip 18" Shoulder to hem 39" Pictures are part of the description. Thanks for looking.