Your question is predicated on an idea that the mark will be placed upon dead people.
I question these visions reliability. Dead people do not buy or sell- the reason for the mark.
Also, the mark is something that is “Received” –this indicates an agreement with the receiver to take it. That is beyond possibility when someone has died.
There was an interesting post yesterday on RFTH quoting Walid the X terrorist, that the mark is the symbol of Islam which is currently worn on a headband or armband. The word translated “In” (the head or hand) is actually “On” in the original meaning, according to the article
. Very interesting, that the only unforgivable sin is blasphemy against the Holy Spirit- not the act of taking the mark. But taking the mark is the outward symbol of the inward blasphemy that the wearer has already done in his heart. This was one of the thoughts conveyed in the article.