It's already registered in Numista.
On 1920, the approximate date of casting of the medal, Charles Picard was the president of the Athens-Piraeus Action Committee of the Alliance française, an institution focused on the propagation of French culture in Greece and the Levant (Near East).
While Numista is not an evaluation site, I will still help you a bit here.
I got mine - the one entered in Numista (which is heavier than yours) from Athens for 15 Euros maybe 10 years ago. But then mine is not in a good condition and the prices do not mean anything; will change for example in an auction with the right audience, but for such a medal, I guess the top will be 75-100 euros, probably much less, around 50, I guess. The subject, artist, issuing authority and rarity really determines these. Our medals fail at all of these:) Rarity? well you got one more:)