My favorite postcard site, Metropolitan Postcard Club of New York City, describes O. de Rycker (1895-1928; Brussels, Belgium) as a " master lithographer," "one of the most famous producers of posters in Europe," and adds, "They also printed many artist signed postcards chromolithography ... ." It is almost impossible to see but on the left edge of this gorgeous Art Nouveau postcard, there is Rycker's publisher's marks.
No artist name is given but this lovely lady with the chrysanthemums is attributed to Fernand Toussaint (1873-1956).
This is an advertising postcard for Gala Peter, a Nestle milk chocolate bar! This card was mailed in Switzerland (Helvetia) in 1904.
The top right corner has a light crease as does the bottom left corner. There are two impression lines: one across her dress sleeve and one that goes up her arm about an inch. However, as you look at the scans and photos, I think you'll agree that the overall impression is one of antique beauty! It's in almost excellent used condition for its age.
Size: about 3.5 by 5.5 inches.
I have a second Gala Peter postcard listed here: http://www.rubylane.com/item/274812-7520/Art-Nouveau-Lithograph-LA-ROSE