On the occasion of the 50th Congress of the Federation of French Philatelic Societies, which was held at Annecy, in France from May 28-30, 1977, the postal department of France issued this first day cover and the stamp on it with a special postmark.
The Château d'Annecy, shown on the stamp, is a restored castle which dominates the old French town of Annecy in the Haute-Savoie département. It was bought by the town, restored and transformed into a museum, le musée-château d'Annecy. The castle is listed as a monument historique by the French Ministry of Culture.
My friend Merja gave me this FDC.