These are an example of a standard issue brass "U.S." national uniform collar insignia.
This insignia was worn by Dr. Thomas N. Weems. He served as a navigator on a Martin B-26 Marauder “Winsockie” of 69th Bombardment Squadron. The “Winsockie” was one of the two B-26s of the 69th Bombardment Squadron assigned to Midway Island in June 1942.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.