(very) Retro AltBoobWorld : The Countess of Somerset. But is she actually wearing an open-fronted dress? The shape suggests she is, though she also has shoulder-boobs. Perhaps it's the corset.
Welcome, new subscribers, to AltBoobWorld! Its the Alt Universe where it's commonplace to wear clothing that shows the boobs. It's not sexual, it's not flashing - it's fashion! (See comments for a little bit more info). Welcome, all!