Modern Military Dog Tags. By the beginning of World War I, the "dog tag" as we know it began to take shape. Soldiers deploying to fight in the trenches of WWI were given two coin-like metal discs ...

My sources tell me that two-holed dog tags were used by the U.S. Marine Corps and U.S. Navy from around 1917 through World War II. The oval tags first came into use around 1917.