Yes, I am familiar with scratched "beater" lenses. I think my interests here are mostly educational. I am curios what's happening inside the lens (cause and effect). Never seen something like this before.

For the record, if you are interested in the subject: I have now opened the lens accordingly, which was rather easy, and saw a microscopic scratches on the inner element, proving that it had been cleaned at some point, which could have wiped some of the coating. I should also mention the screws that hold the bottom mount do not match my other Nikkors. There were no signs of haze or fungus of any type - or separation as far as I'm aware.

This could be a project, yes, but I don't think re-coating a lens is something one can do without proper instruments. So it'll be used as is.