Is There a Way to Know if a Manuscript is the “Original”?

In response to the recent flurry of posts on the question of a “first-century Mark,” I have received a very interesting question: suppose there *were* a first-century Mark that was discovered (hey, it’s possible!  And we’re holding our breaths – what an amazing find it would be)..  Would there be a way of showing it was the actual original Mark, the one the author himself wrote with his own hand?

I was asked this question on the blog seven years ago, and responded to it by saying I had never...