Vintage Gloria Vanderbilt shirt/blouse.Lightweight blue cotton denim.VGC.Says size L.
But definitely not.I was approx a UK 12 when I wore this.
Armpit to armpit across the back 20 1/2 inch.Slightly fitted.Poppered stud fastening.Bought by myself in USA in the 1990s.Checked cotton lined neck and yoke inside,match the back detail.