What does Les believe the mark of the beast is?
The mark of the beast is understood as a computer number, a credit card type thing, or a transaction card. It is described as already in common use in Europe, containing health records and bank balances, and seen as a stepping stone to the actual mark.
Les explains that the mark of the beast is a number—a computer number, a credit card type thing, or a transaction card. He cites a card now used in Europe that contains your health record, bank balance, and everything pertaining to everyday experience. He sees this as a stepping stone to the actual mark. Once people accept it, Revelation 16:2 says a noisome and grievous sore falls upon those who had the mark and worshipped the beast's image.
And the first went, and poured out his vial upon the earth; and there fell a noisome and grievous sore upon the men which had the mark of the beast, and upon them which worshipped his image.