Found this cute dress at a peddlers mall, looks 40s to me but wondering if it's more late 30s or where in the 40s you would date it? It closes with a row of buttons on the side, no zippers. Also it has some dark brown and yellow spots on it what's the safest way to clean it? I'm pretty sure it's cotton or a cotton blend. I wish it fit me but its on my extra small mannequin. Thanks guys!