- According to Robert Osborne’s BECNT commentary on Revelation, “a brand or tattoo on the forehead of a slave was common in the ancient world as a sign of ownership, and there were also religious tattoos to show allegiance to a particular god” (p. 310). As one example, Petronius (first century CE) wrote: “Then I will come and mark your foreheads with some neat inscription so that you will look like slaves punished by branding” (Satyricon, 103). Martial (Epigrams 2.29.9–10) also mocked a manumitted slave who tried to hide branding scars on his forehead with a rather long fringe. John of Patmos drew on this imagery in Revelation, both with respect to the followers of the Beast having identifying marks on their forehead and hands, as well as the followers of the Lamb with a seal on their foreheads (7:3, 13:16-17). Paul also portrayed Christians as slaves of God (Romans 6:1-23), who “set his seal of ownership on us, and put his Spirit in our hearts as a deposit” (2 Corinthians 1:22; cf. Ephesians 1:13-14, 4:29-30 on Christians stamped with the seal of the Holy Spirit). For more on the branding and tattooing of slaves, see C. P. Jones’ 1987 article in Journal of Roman Studies. However not all slaves were identifiable in this manner. Other than overt marking, slaves usually wore simple tunics while masters often wore togas, domestic slaves were also sometimes dressed rather effeminately as a sign of their status. This is a much more subjective matter than physical marking (or bearing scars from beatings), and classical literature has a number of stories about citizens disguising themselves as slaves and vice versa. Here is a thesis on runaway slaves in Roman society and it mentions one example of a senator who swapped clothes with his slave, thereby evading an assassination attempt.
- https://studenttheses.universiteitleiden.nl/handle/1887/74843