Definitely NOT the "mark of the beast"
That is spiritual language! Read Revelation 14:1...do you think that there will be a physical mark of God's children on their forehead? Nope!
The mark of the beast is something that is saying in essence " I will not serve Christ, but I will serve this world and all that it has to offer at all costs and to whom ever I must.... but not Christ!
It is from the heart, not a physical mark.
All the world is already bearing either the mark of the beast, or the mark of Christ.
God Himself knows who they are and they will be seperated as sheep from the goats come harvest time!
" In Thee O Lord do I put my trust " ~ Psalm 31:1~