I was curious about the badge as I recognized it is not the standard FrenchArmy insignia, that does display the "RF" for Republic of France, but has the addition of an anchor in the design.
From a very brief review of Adrian helmets online I concur this is a model 1915 (because of the construction of the edge from separate pieces). I did find an interesting story behind the cap piece that by WWI was worn by French colonial troops, which is the information I was interested in.
Short of declaring the helmet authentic, my uneducated opinion is it is authentic, that someone probably relined and used it as a safety helmet. It would be interesting to know if a colonial troops cap badge would be more valuable than any of the several other cap badges that were used on Adrian helmets, and therefore worth the effort to replicate.