I think the decalhelmet.com website's info about that particular helmet is partially incorrect. The "flaming bombshell" emblem has been the insignia of the Artillery Ordnance Department of the French Army for the past two centuries. (Also, as a token of respect for French assistance in the RevWar and the prowess of the french Army under Napoleon, the US Army adopted the "flaming bombshell" emblem for its Ordnance Corps buttons in 1832, and that emblem remained on US Ordnance Corps buttons until 1902.)
According to Wikipedia, Gendarmerie is a French word for "a military force charged with police duties among civilian populations." It seems strange that the emblem of the French Artillery Ordnance Department would be on a helmet intended for Gendarmerie use. Still, I suppose anything is possible in the French army. ;-)
But at least Ramswin (the original poster) will now know what the emblem on that helmet represents. The letters "RF" on the emblem presumably stand for "Republique Francais" ...meaning, the Republic Of France.