On the Petersham of the Gown it states:
" By Special Appointment DRESSMAKER to H.R.H. Princess of Wales ELISE 170 Regent St London"
In 1870, the Monarch was Queen Victorian, and she was Queen of the United Kingdom of Great Britain and Ireland. What I find of further interest in regards to this gown is that the wearer appears to be rather tall, and Queen Victoria certainly was not, as I have seen one of her gowns at the FIDM exhibit this year. Enjoy!