Could we have a look at the back, Caz? What a sweet photo!
I have a Vanderbilt but it's Canadian. There are a couple of EJ Vanderbilt photos on the web but they don't look anything like this guy's cardstock...they're all fancy-like.
There had been white wedding dresses for quite some time but as this is a sepia photo we can't really be sure this one is white. Looks like white, but could be any pastel I suppose. I could totally see myself wearing it, on a dreamy warm afternoon, sitting on the lawn by a willow tree with Lady Cora while Barrow serves us tea. Although I'd rather it were Bates serving the tea

Hairstyle is vaguely early 20s. I need to see the hemline

Cheers,
China