Vintage 1970's Joseph Magnin navy blue drape dress

Great vintage 1970's v drape in front & back, long sleeve dress. It's hard to find one similar online, so you will be on of a kind in this cool dress. 100% acrylic with shoulder pads. There's no size inside on the tags. The approximate measurements are, armpit to armpit: 20 1/2 waist : 18 1/2 My guess is it's a medium -large