Powder pink dress jacket fitted Sz Small vintage

I’m not sure of the age off this jacket, it’sjust been sitting in my closet . Size of the jacket states Medium but it fits like a small. Dimensions laying flat.. Approx: shoulder to shoulder 15”, armpit 16”,waist 14” . Length of sleeve 23.5. Jacket is in great condition. Materials: 97% cotton, 3% spandex.