Need Help Dating This Army Officer "US" Insignia

[usmedalman]

I received a grouping of miscellaneous items for an officer who was commissioned in 1926 and retired in 1947. Could someone please help determine the date when this style of insignia was used and also the sort of rank (subdued or shiny) that would pair with it? Also, would branch insignia have been worn with this also?

 

Thanks in advance for your help.

 

 

[268th C.A.]

World War 1 

[268th C.A.]

Yes this would have been worn on the collar with the branch of service behind it. A US and BOS on both right & Left sides as pictured