Yes I'm inclined to agree with Gayle it may be on the manni backwards, there are no bust darts on the side you have shown from the front, causing the arms to gape somewhat. I take it there is no fastening at the top of the neck too?
I have a 1950's dress that has a chiffon overdress that fastens at the front with only a hook and eye (and then a matching belt goes over this).