This never ever used (although tried out) outfit and coat was bought by my aunt in the 1960s in Washington, DC for $250. She never ever wore it and offered it to me some years ago, wishing I would use it. I have never ever worn it. There are no labels, so I do not know if it is a designer outfit, but it seems-- a vintage clothing person told me it appeared like an early Bill Blass. It has beadwork at the neckline and at the hem; the beads are plastic, not crystal and are mounted on a silvery trim in clusters of 5, to appear flowerlike, with sparkly leaves and "gems." The pronounced A joints on jacket front and gown front mark it as extremely 1960s. Among the sparkly buttons is missing one rhinestone/gem.
The size is marked 12, however I would size it a 4-6 or small 8-- 17-18" from underarm to armpit, 34" waist. Sizes have actually altered given that the 1960s. The fabric is heavy, cut on the bias; you would have to have this dry cleaned extremely carefully since of the trim. Length would fall right above the knee-- 38" from neck to hem. This is a beautiful vintage piece!