How do you stop a thief?

This was the question that vexed a rugged Marine. Every morning he picked up coffee from a machine, and every morning that cup of
coffee mysteriously
disappeared from his desk. Although he never caught the bandit, he did resolve the matter. One morning, when all
personnel were gathered
for a staff meeting, he popped out a denture from his mouth and swished it around in his coffee before placing
it back.
His coffee was never stolen again.