Rank insignia of Amiral de France for the French Navy, used in World War I
Own work, based on:

(1918)  Military And Naval Recognition Book: A Handbook On The Organization, Uniforms And Insignia Of Rank Of The World's Armed Forces (2nd ed.), Category:New York:  D. Van Nostrand Company, p. 167  
(1918)  Army and Navy Uniforms and Insignia, New York, N.Y.:  Frederick A. Stokes Company, p. 242