Weel....
You just don't find a lot of Spacemaker 30's, so there's that.
IF it checked out to be in really great shape, with few or no restoration hassles, it might be worth the $300 asked - and remember, negotiation is always possible.
One plus here is that this range does not - and evidently never had - Automatic Calrod on the large burner. That saves a lengthy, expensive parts search right there, because Automatic Calrod units are pretty usually kaput. And it also saves frustration, because sometimes you just can't find parts, and you either have to live with a defunct burner, which is bad for cooking, or have to convert it to a regular burner, which is bad for authenticity. This range side-steps all those issues.
So, depending on the depth of your desire for a Spacemaker 30 and the depth of your pockets, this might be a decent deal with some dickering.