This coin is quite likely UNIQUE. Unlike most French essay (trial) or proof coins that are struck in aluminum, this one is struck in silver or silver-plated brass or bronze, judging by its considerable weight (almost 20 grams).

Moreover, the design is also unique.  The bust of Ceres bears some similarity to the 1849-1851 5 Franc coin but differs in numerous details. The back is completely different.

We could find no listing of this coin on eBay or elsewhere. Unlisted in Mazard.

As beautiful as it is rare. A true trophy coin!