Spring flowers, a trio of fish and a small child, it must be the 1st April in France, or Poisson d'Avril. The tradition is of children sticking a paper fish on the back of an adult and running away shouting 'Poisson d'Avril' (April Fish). At the beginning of the 20th century it was very popular to send these fishy cards in the post and you can see more, with an explanation of the tradition on The Daily Postcard. This card was sent to Béthune in Northern France
on 31st March 1911 and no doubt Monsieur Robert Delemaire would smile as he received it on April Fool's Day. I love these wacky cards, I wonder if anyone still sends them.