The basic ID (US Army 14th Infantry Regiment) is correct. But the fact that the letters "US" and number "14" are applied to the brass disc means it dates strictly from 1937-to-1943. For confirmation, go to: Dating Metallic Insignia: Collar Disks
and scroll down the the section titled "Type III disks 1937-1943" where you'll see info and photos showing examples of the 1937-43 type.