Minorca is one of the Balearic Islands located in the Mediterranean Sea belonging to Spain. The island is the second largest of the Balearic Islands, located to the northeast of Mallorca.
October 8, 1993 the island of Minorca was declared a Biosphere Reserve by UNESCO.
Coming from Spain with "Swiss" stamps...weird^^
It's a private courier service, some souvenir shops offer Swiss Post stamps. There are special boxes in which postcards franked with those stamps have to be posted. Swiss post collect them and sent the postcards.
From a Minorca P.P. Sheet of 10 Post Paid labels Swiss Post International