My grandfather's ring

Does any one know the "identity" of the insignia engraved, and pretty heavily worn, on this ring??
I have a ring that belonged to my maternal grandfather who was a US soldier during WW1.
He was "Mustard" gassed, and survived, in the Argonne forest of France.
This is all documented.
Anyway I have a ring he wore that I believe MAY be some form of military ring but has been worn to NEARLY the point of being unrecognizable as to its origin and true "identity".
It is a distinctly two metal ring with what appears to be a very worn , possibly military, insignia engraved into the yellow metal portion of the ring.
Could/ would anyone, be able to give an educated guess as to what the ring's insignia is??
I am NOT interested in selling it. It is so worn that it would have very little intrinsic value.
I simply want to know its "identity" as part of my heritage.
I look forward to hearing from you soon.