Vintage 1970s Blue Butterfly Short Sleeve Button Down Blouse

Measurements laid flat: Shoulder seam to shoulder seam: 15" Armpit to armpit: 17" Sleeve opening: 6" Length from shoulder to hem: 24.5" Short sleeve button down shirt with a cloverleaf collar and cuffed short sleeves. All over butterfly print in blue. The brand label is "Ah! Austin Hill." There is an ILGWU label (International Ladies Garment Workers Union) estimated as dating from the late 70s-possibly early 80s. It is marked a size 8, but please check measurements because it's smaller than a modern 8. No fiber content label. It feels like a nylon or other synthetic blend with maybe some cotton. Fabric doesn't stretch. It's slightly sheer, in excellent vintage condition with no fading, stains or holes.