This is a blue cape or swing-style jacket from Helene Berman. It is a size XS.
It has a double-breasted button front with 4 buttons. When laid flat it measures 21.5" from the back of neck to hem, 18" underarm to underarm and 17" from shoulder to cuff and 14.75" shoulder to shoulder.
It is made of a cotton elastane blend and is in great pre-owned condition.