Vintage Miss Shaheen Fish and Exploration sail dress

Size unknown but looks to be a 10-12 or L/XL. Material tag is well worn but feels like a polyester mix. There is some stretch in the material and the buttons on the front is functioning but likely used to slip on. Some signs of wear and pilling but no rips, tears or stains. Laid flat the pit to pit is 18 inches across, waist is 18.25 and hips is 21 inches across.