Photo: Wikimedia Commons/Gloumouth1
Children’s Toy: When Allied paratroopers jumped into Normandy on D-Day, they needed a way to identify each other in the dark behind German lines. Military planners came up with brass versions of a common children’s toy, the cricket noise maker. Troops would click the noisemaker while near an unknown person in the dark. If the other person responded with a click or code word, the soldiers knew each other as friendly.