Great vintage dress!  There's no size tag.  MEDIUM is an estimate.  Photos taken on a size two mannequin.  

Asymmetric neckline.  Slightly padded shoulders.  Pullover.  Tiered skirt.  

Approximate measurements:

Chest pit to pit 20”

Waist across 18.5”

Hips across 19.5”

Shoulder to shoulder 14.5”