Victorian Harrach Peach Pink Opalescent Enamelled Perfume Bottle

This is such a delicate piece. This stands about 4" and is missing a stopper. I would love to know what the stopper looked like. The enamelling is so beautifully executed. This perfume bottle goes from and opaque peach to a light pink opaline. The pontil shows a painted number 6 or 9. I would love to learn anything more about this piece. Special thanks to my good friend and collector whom was gracious enough to let this lovely piece go to a good home :). Thanks for looking