While on vacation, looking in antique stores, I came across what I thought was a glass plate negative on dark brown glass. It was cheap, so I had to buy it. Upon closer inspection, I realized it was a positive image. I've never seen one of these, and have no real experience with glass plates. The image looks to be of two women in victorian type dress. It looks like it might have been mounted in some type of case at one time. I don't believe it's a dag, as it doesn't have any of their characteristics, but I really don't know what it is, or how this was used. Anybody have any ideas?