Thank to a Postcrossing, this definitive Swiss stamp arrived at home : its denomination indicates it is valid for a postcard sent to an European country.
A tour inside the Swiss Post website helps to retrieve lots of intels :
* the blue stamp is in the list of valid stamps inside the pdf file "Ordinary stamps 1977+". It was issued in 2002 with another red one, that is valid for a worldwide card. The same year, you can look for one already-seen-on-this-blog insect.
* Europe, Swiss postal rate-ly speaking (.pdf) goes to Russia, Turkey and Greenland.
* The prioritary letter less than 20 grams to Europe needs a 1,30 Swiss franc stampage (around 0,79 € or 1,08 USD). Economic rate is not interesting in this case : 1,20 CHF (0,73 € or 0,99 USD).
A more profound research finds the initial presentation of this stamp : "Special stamps for card sent abroad". These bleu and red stamps are sold in booklet of six, with a discount (0,60 CHF for a six-blue-stamp booklet, 0,80 CHF for the red version). The discount is made possible because these two stamps can only be used for postcards, not letters (read the message inside a booklet).
The illustration is the emblem of the Tourist office of Swiss.
These stamps help greatly the foreign tourists in Swiss, with a discount. We all are not patient or interested enough to take time and discover the philatelic state of a post office during our holidays.
An award for the quality and content of the Swiss Post website.