Ecu - An Old French coin with a shield as its central device. Gold coin worth 3 livres from the 14th century until the introduction of the louis d'or in 1640. A silver, crown-sized coin issued in 1642 at 3 livres but later varied between 5, 6 and 8 livres. Silver piece worth 5 francs after the franc was first issued in 1795. Also, a 20-franc silver piece minted from 1929 to 1938. So called because it bore on its one face 3 fleurs-de-lis, like a heraldic shield.