With the help of Jeff Floyd, this medal appears to be a WWI French Regimental or Battalion medal, the 9th S___ Rmt/Btn. Is there a source /list of french regiments/battalions in WWI? Even basic information would help. I now know that it is from the French 9th___S Regiment or Battallion. UNKNOWN%20NECK%20CROSS.JPG UNKNOWN%20NECK%20CROSS%20REVERSE.JPG
I would hazard a guess that the S might be "Sapeurs".
The only drawback to my speculation is that the Génie used a trophy of arms as their badge (my great-uncle served in the Engineers, and this is on his adrien helmet), and not crossed swords.