One way to help determine live ink in this context is to get the glare of a lamp directly on the ink and the photo behind it. If the black ink turns orange or some such, that is not a preprint pr reprint (of course, although not in question here, an Autopen signature would also turn color as it is signed by a machine holding any pen you give it).
I think the trick with auto pens is the pressure and a tell tail dot either beginning or ending?...I am hoping my microscope camera can see a difference as a human hand will show different pressures in the sig.
It may well do so, but that may have little to do with just whose hand (speaking generally, forest/trees etc). I think the concern here was live ink vs a reprint/preprint.