What Is the Mark of the Beast?

Some manuscripts have the number of the beast as 616. That's easily explained by a variant spelling of Nero. So it looks like someone in the very early church, first and second century knew that this was Nero and they used an alternate spelling to spell him. It should be essentially what the mark of the beast was in its primary fulfillment back in the first century. But I think sometimes people can get really myopically focused in reading this, always rushing to map it onto a present event.