Your dress seems to be late '40s, I think and I wonder if the straps were altered: the bodice seems to sit up very high so perhaps someone shortened the straps to make it more modest or for a very short woman or child. I recommend that you check if the length is still there because it could be worth returning it to the original style. You'd have to be very flat chested to wear it as is, and the gaping at the centre back neckline also suggests it was altered as it should sit flatter across your back.