Please don't take this the wrong way but I think it's a genuine Katrinka's or Wenger SAK. I'm a member of the SOSAK forum and I've never seen a genuine SAK with both a corkscrew and a Phillips screwdriver on the back tools.
The the rivets are another point, on a Vitorinox or Wenger they are made of brass rods with brass collars at both ends, so unless it's a custom made or mod'd SAK I would have to say that its not the genuine article.
The only way to make sure is to look at the tang at the base of the main blade when its open.