Mark of slaves Slaves were also known to wear dog tags on their person, typically in the form of an unremovable metal collar that would be inscribed with messages such as: If you find this slave, he has run away. Please return him to his owner at the following address. You will be rewarded. These, along with branding and tattooing, were common ways for Roman slaves to be separated from the rest of the Roman social system, and easily punishable should they make their escape.