I will keep a look our for any further hints of the maker essi.
One of the problems with these lovely pieces of art glass is the fact that the Words Nuurajarvi Notsjo , so beautifully written, are not the signature of the maker, and neither are they inscribed by the maker of the piece, but by another member of staff, so all my lovely pieces by Jaakko Niemi have the Nuutajarvi Notsjo words in the very same handwriting, and indeed they also have Jaakko Niemi's name written in the same writing, so that does not help you at all.
I am desperately trying to think of another glass artist who might have worked for Nuutajarvi Notsjo with the initials FK.... but I agree that it does look more like a Jaakko Niemi design, and had there been no other initials on it I wouldn't have given it a second though.
Intriguing!