Vintage Blue Hostess/Cocktail Dress

I believe this to be a private/home seamstress who made this. No tags for size, brand or fabric content. Feels polyester. Gorgeous true blue color, excellent and flawless condition. Not sure what you call that neckline, but it’s very retro. Nice darting work under the breast line too. Pit to pit: 17”, high waist:15”, widest part of dress/hips: 21”. Total length shoulder to bottom hem: 52”. Back zip closure.