Departure marking La Feré Aisne. (Departement: Aisne)
La Feré is around 75km from the Belgian border
The cover has a 4 juin 1940 stamped date.
The letter indicates return to sender with the blue crayon markings.
This was because of the German invasion of France. Apparently all mail
service was discontinued at that moment.
Departure marking Mirecourt (Vosges)
Arrival marking Molsheim