Help I.D. What era? War pin

[olekyground]

I found what I think is a pin. It reads U.S. and in the small box "NG" 138 under that.

Any ideas what it is or how old? thanks!

 

[kansas coin hunter]

its a world one or early 40s but i iam gonna say world one national guerid collar insegnia

 

[chrisplay2004]

Agreed on U.S. National Guard 138 regimend
but dates closer to 1917-1918

 

[olekyground]

Sweet now I can put it in my display case. thanks guys!!