The date is provided by the very reliable carolath habsburg.
From carolathhabsburg.tumblr.com-post-131555288937-princess-isabelle-d-orleans-later-duchess-of. I decided not to post this when I first saw it because the image was so grainy that the sleeves and some of the neckline blended into the background and the neckline was very high. I did not understand what I was seeing, the neckline, or where her shoulder were. However, the last image cleared up the questions of where the shoulders and sleeves belong and where is the neckline. So I removed the splotches in the background entirely and replaced them with a generic background, removed spots in her hair, on her face, and on her dress and print with Photoshop and removed the monocolor tint. The image has been enlarged one third. Also posted to Isabelle d’Orléans, duchesse de Guise’s Subalbum here.