This is one of three Gala Peter postcards I have available. The chrysanthemum card in the series is listed here: http://www.rubylane.com/item/274812-7424/Art-Nouveau-Lithograph-Le-Chrsyanteme and the sunflower lady is here: https://www.rubylane.com/item/274812-7888/Art-Nouveau-Gala-Peter-French-Advertising
This is an advertising postcard for Gala Peter, a Nestle milk chocolate bar! "... pour croquer le premier des chocolats au lait -- for the first bite of milk chocolate."
No artist name is given but this lovely lady who is stopping to smell the rose is often attributed to Raphael Kirchner (1876 - 1917). Unfortunately, the plight of many artists during postcard's Golden Age was for their work to go uncredited by the advertiser they designed for.
It is almost impossible to see (I had to get out my jeweler's loupe) but on the left edge of this gorgeous Art Nouveau postcard, there is printed "Lith O. De Rycker Mende Brussels." My favorite postcard site, Metropolitan Postcard Club of New York City, describes O. de Rycker (1895-1928) as a " master lithographer," "one of the most famous producers of posters in Europe," and adds, "They also printed many artist signed postcards chromolithography ... ."
With an undivided back, this card dates to 1903 or earlier. It is in overall near mint unused condition. To be uber nit-picky, the only thing I could see that merits mention is a paper "patch" in her hair. Also, please note that the direct scan (first picture) accurately shows the antique off-white/light cream color of the card. In the photos (second and third pictures) the card looks whiter than it really is. Size: about 3.5 by 5.5 inches.