Following are excerpts from "French Gold Rooster Investor Education - Mint State Gold...
The use of the Gallic Rooster as a symbol came to France from the Romans. In 58-52 BCE, the Roman's conquered the region and named it Gallia (Gaul). This sounded similar to another Roman word galus meaning rooster. Because of the similarity between the two, Gaul would be confused with galus and so the association stuck.
In the 6th century CE, the Germanic Franks would conquer the Roman province. In the 14th century, coins were inscribed with Francorum Rex (King of the Frank's in deference to the reign of Jean le Bon (1350-64). By 1795 franc became the official name of the currency.
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On the coin's obverse is an image of Marianne, a personification of liberty and reason and the national symbol of the French Republic; on the reverse is the rooster, the unofficial symbol of French pride and culture.
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Reliefs on both sides of the Rooster were created by legendary French sculptor, medalist and presidential portraitist of France, Jules Clement Chaplain; the rooster is known to the French as le coq gaulois; his medals for Nicholas and Alexandria of Russia were said to be the finest ever struck.... Since 1878, the Monnaie de Paris has been the sole French mint producing coins.