U.S. D-Day Signaling Cricket / Clacker

D-Day is a term often used in military parlance to denote the day on which a combat attack or operation is to be initiated. "D-Day" often represents a variable, designating the day upon which some significant event will occur or has occurred; see Military designation of days and hours for similar terms.
US Paratroopers were issued these clicking "Crickets" which were intended for use to communicate with other Airborne Troops in the total darkness of night immediately preceding the landings on June 6th, 1944. The paratroopers were free to hang their cricket wherever they wished. Some have kept it in the pockets of their jackets or their pants, others have hung it around the neck or on their helmet. Nowadays, many reproductions have been produced and it is not uncommon to hear "click-clack" in the commemorative ceremonies in Normandy.