23mm, General Staff Officer coat button, dug,  with a ".*.Extra.*./Gilt" backmark. This is a very unusual Federal Staff Officer's button.  There are 30 stars encircling the eagle which holds four arrows in left talon (reversed from many).  I recall when Bob Edmondson picked up an example of this and shared with excitement many years ago at the Nashville Show when held at the Fairgrounds.  I have seen two or three of these nondug and they were not gilded, but left in brass finish.