I really love the way this oversized, top fits. It has a structured look to it, mainly because it is in pristine, most likely never worn, vintage condition. It will probably soften up over time and washing, but I actually love the way it holds its shape. It's a beautiful deep dark olive green colour. I would wear this the same as I would a light blazer.
I would call this a Small / Medium with a mellow styling. As usual please refer to the below measurements for most accurate fit.
Item Measurements: Laying Flat / Not Doubled / Not Stretched
Shoulder seam to shoulder seam width: 15.75 inches wide
Armpit seam to armpit seam width: 20.5 inches wide
Armpit hole length: 9.5 inches long
Sleeve length: 24.5 inches long
Waist width: 20.5 inches wide
Hem width: 22 inches wide
Length of garment from shoulder seam to hem: 28.25 inches long