Spiegel did indeed have sling swivels installed.
So the only concerns I have would be the amount of wear on the bluing. There is a small rust spot on the under side of the barrel. I think 400 would be a buy.
$500 is a buy, $400 is a crime.
Why not just cut the crap and offer him $100 and a bottle of Jim Beam, after you drink half the bottle with him?