What do you reckon $500 or $600 depending on condition, maybe more, maybe less?

Not one of the better 70's Williams games.  Playfield looks like Jubilee/Darling with inlanes instead of the ball kickers.

The red in Sky Lab is usually faded out on the backglass.

Not something i'd consider owning, so hard to put a price on it.  Ebay would be the best judge.