This very rare and special green enamel floral marcasite brooch from, Paris.
Although unlike much of his work, this appears to be by Antoine Bricteux who specialized in producing Art Nouveau jewels c.1900. He worked with G. Landois."Genre Lalique". Although difficult to read, it is marked with an eagle's head (which indicates a gold purity of at least 18 karat) and the words Made in France, the placement of the mark makes it impossible to positively identify the maker. Because it is white gold, that places this brooch c. 1911.
Measuring approximately two inches high by one and one quarter inch at the wide end of the fan, it is in excellent antique condition with the exception of missing three small marcasites (priced accordingly).