The collar was worn during the St. Mihiel operation.
The latest discovery is unfortunately the evidence.
A friend of mine found 2 USMC collar discs of the same type ( supposedly french made) in the woods South of Exermont (Argonne) where the 4Th Brigade was billeted before the 3 rd phase of the Meuse Argonne offensive (last week of October 1918) See Mc Leeland book
In the same wood( MXXXeau wood) I found 3 EG&A Mod 1914 Emblems and my friend much more but not during the same year
I have the pictures taken on the spot, but only on slide format ( circa 1990)