Service members have long been issued two identical dog tags. What was the original reason for the second one?

The answer is C: One stayed with the fallen, one went to records for burial

Starting in 1916, the Army issued two tags so that if a soldier was killed, one tag stayed with the body for identification while the other went to record-keepers for the burial service. The redundancy meant no one would be lost as 'unknown' if a single tag went missing.