It is not a slant shank machine.
The older Necchi machines are highly regarded, and that one looks like a great machine, but I personally wouldn't buy it without being able to make sure everything works.
The older Necchis were made to very close tolerances, and as such needed regular oiling to remain in tip top sewing condition. Not to say that the one shown isn't, or couldn't be returned to that condition.
That said, if you don't mind possibly having to tinker with a machine, and the price works for you, Necchis are very nice machines.