A guidon is a pennant-shaped standard that signifies a particular unit. Modern U.S. Air Force guidons are ultramarine blue and yellow. The parent unit name appears at the top and the squadron name below. In the middle is an eagle.
This early guidon is made of dark blue fabric with a yellow felt eagle and lettering.
From their beginnings as Military Police in WWII to Air Police and then to Security Police, today the protectors of U.S. Air Force personnel and assets are known as Security Forces.