Very nice US "Son-In-Service" badge featuring three stars. Workin pin and catch on the reverse. Clearly dated with a 1917 patent. No enamel damage present. Roughly 0.75 inches in width, quite small.
 
A service flag or service banner is a banner that family members of those serving in the United States Armed Forces can display. The flag or banner is officially defined as a white field with a red border, with a blue star for each family member serving in the Armed Forces of the United States during any period of war or hostilities. A gold star (with a blue edge) represents a family member who died during military operations, including those who lost their lives during World War I, World War II, or any subsequent period of armed hostilities in which the United States was engaged before July 1, 1958, and those who lost or lose their lives after June 30, 1958: