You know the mark will be on the right hand or forehead. if you don't have a right hand. Noticed, King James Version says
IN and the other translations say
ON
Just speculating, does IN mean with a chip or in the blood? ON to me would be a visible mark.
I think either way, the mark will be scannable and or seen in order to buy or sell.
KJV
16 And he causeth all, both small and great, rich and poor, free and bond, to receive a mark in their right hand, or in their foreheads:
17 And that no man might buy or sell, save he that had the mark, or the name of the beast, or the number of his name.
18 Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number is Six hundred threescore and six.