Here is an interesting read on the "mark"
The Beast’s "Mark"
The Greek word used for "mark" is charagma. It was the technical term for the Roman imperial stamp that appeared on various documents. The charagma was a seal stamped with the name and date of the emperor and attached to commercial documents. Apparently, it also stood for the emperor’s head stamped on coins. Thus, the charagma represented the likeness or name of the emperor.
The charagma was also a type of brand. In Roman times, disobedient slaves were often branded with marks of ownership, much like cattle are today. Religious tattooing was also widespread. Soldiers had a custom of branding themselves with the name of a favorite general. Devotees of a god labeled themselves with tattoos to designate their loyal devotion.
However, we should be careful about looking for some ancient practice of "marking" and thinking that this is what will happen in the future. John was writing to real people in the first-century church, not some "end-time" church, and his message applied to them. Whatever the "mark" was, it conveyed something they could understand.
What point was John trying to get across when he was speaking of a "mark"? The mark is probably not meant to be something visible to the eye, as was the Nazi practice of tattooing numbers on concentration camp inmates. Nor should we assume it to be an identity card of some kind, like a Social Security or credit card.
More likely, the mark is a symbol. It is something that identifies who belongs to the beast – or to God. There is an Old Testament parallel in Ezekiel on which Revelation draws. John’s readers would have readily understood the point he was making. In vision, Ezekiel saw a man with a writing kit at his side. He heard the Lord say to the man, "Go throughout the city of Jerusalem and put a mark on the foreheads of those who grieve and lament over all the detestable things that are done in it" (Ezekiel 9:4). Here are people who are "marked" for protection.
In like manner, Israel was "marked" by blood smeared on the doorposts of their homes. On the eve of the Exodus, the death angel swept through Egypt, killing the firstborn. He passed over any door marked with blood (Exodus 12:21-23). This mark was merely a symbol, as the angel would have been quite able to distinguish between an Israelite and Egyptian.
Earlier in Revelation we read of the 144,000 servants of God who were sealed on their foreheads with "the seal [sphragis] of the living God" (7:2). They were also to be protected from the plagues that would devastate the earth (7:3). Those not having the seal were afforded no protection (9:4).
The "mark of the beast" is a counterpart to the sealing of the faithful people of God. The beast will attempt to identify and protect his people (and destroy his enemies) even as God knows and protects those who are his people.
How does the beast know who are his own? Simple: they are all willing to worship him and his image. Their worship is the mark by which they are identified! Those who refuse to worship will be exposed by their refusal to perform the act of idolatrous obeisance. Their steadfast loyalty to God, however, will be the evidence that they carry the seal of God. The "mark" of the beast is not visible writing, just as the "seal" of God’s servants is not done in writing. It is the behavior of the person that indicates where the person’s allegiance is.
Of course, the refusal to worship the beast will bring serious personal and economic consequences for the people of God. That’s because, "No one could buy or sell unless he had the mark" (13:17). Those who do not worship the beast are not allowed to participate in the economic life of the community.
The false political and religious system wields tight economic control over those whom it dominates. No one is exempt from this harsh economic repression. Whether small, great, rich, poor, free, or slave – all must comply (3:16-17). Individuals who refuse to serve the beast are not allowed to carry out the smallest economic transactions. This has always been a favorite way by which governments and authorities shut out undesirables from the system. They don’t allow them to participate in the benefits of the economy in one way or another.
That means they cannot buy food, obtain shelter, clothing or receive medical help. This implies starvation, exposure and death for those who do not worship the beast.
