Unfortunately I don't have any reference books at work so this is from memory.
The first item is, I think, from when he was at Iittala, and the signature looks similar to Tapio Wirkkala's. The other two where when he was working at Nuutajarvi Notsjo (not sure if he moved firms, or one took over the other).
I would also suggest that the signatures were not done by the designers themselves, and so one would expect the same style of signature to appear for different designers (Gunnel Nyman and Kaj Franck both had acid pen signatures for a while at Nuutajarvi, I think).
This is not to say that the first is genuine, but that the different signature isn't necessarily evidence of a forgery. (but are his pieces from Iittala and Nuutajarvi valued the same ?)