Congratulations! That is a very neat find!
I did a quick google search for the 314th Field Artillery, and the history of Company B actually mentions the machine, and the fact that it was apparently left behind when heading towards the front in September 1918: "disposed of surplus equipment, and this included our
much admired Army and Navy graphophone, which would be of no service
to us..." (Aside from the incorrect "graphophone", I assume the passage refers to the Edison)
The full unit history can be found here:
http://www.wvgenweb.org/marshall/314/314-memoriesb.txt