In bronze gilt with silvered wreath, officially hand stamped on reverse with number B10031, which dates it early to mid 1918.
All badges issued during WWI were serial numbered and carried an official hallmark of a framed capital ‘B’, followed by the number. The first production series of roughly 7000 had slightly smaller numerals, while the second series of around 8,000 had larger. This one is the second series and dates to early/mid 1918 when comparing to known badges to corresponding pilots.
French Military Pilot Brevets (pilot qualification certificate) from 1911 to November 1918 totalled 17,034 and around 22,000 ‘B’ numbered pilot badges issued from 1916 to 1925. Comparing badges with numbers of known badges with dates, would suggest anything less that numbered 12,500 is WW1 and certainly the higher numbers are nearer 1925.