The 15-IOW Infantry Officers Whistle WWI WWII. Nickel-Plated Brass. High quality. Hang on your key chain or neck for security. Dimensions: 3 1/4" long, 1/2" diameter. Marked with the Ministry of Defense's "Broad Arrow" and dated "1916". This whistle is an exact replica of the whistle used by officers to signal for the troops to "go over the top".