7/8" with tiny union bug at 6 o'clock. A few other Winchester World War II buttons are known. This one  features their logo of the era, a bold red "W", on a button given employees who bought bonds in the drive to raise 15 billion dollars between Roosevelt's announcement Sept 8, 1943 and the close on October 2, 1943.  The goal was exceeded by 4 billion with total topping 19 billion. Only example known to us. Glossy and Exc.