Can you take a clearer photograph of the label? The style of the dress doesn't look like 1951 to me, it looks more like 1959. The stains under the arms will hurt the value a lot because it isn't a wearable, but as a collectable, it would still have value. It would be worth your while to have it properly evaluated. Don't be cheap - spend the money to get a proper authentication done - it's worth the investment. If you can, take better photos and send it to Kerry Taylor in London, or Karen Augusta in Vermont, or Linda Hindeman in Chicago and ask for an authentication, or a place where you can send it to be authenticated. Museums won't do it, and the designer shops won't know - HQ will, but you won't find anyone there who will talk to you. Unless you are a curator from a major museum, they don't have time.