Thank you so much for contributing, m!!
I was already a little bit frustrated that no one had any ideas regarding this beautiful vase...
I had already looked into the Bo Borgström designs (and have to admit that there are similarities regarding the style -- and some daring colour combos as well

.
What put me off was that I couln't find anything in this unusual amethyst-grey colour nor a similar shape, that the casing in my vase is almost half its total height, and the different finished base and rim. (Well, thanks for checking yours, so the cut rim wouldn't rule it out).
In another thread here is a base shot of an Aseda vase
http://www.glassmessages.com/index.php/topic,33074.0.html, which looks nothing like the ground and bevelled base my vase has.
But I will research this further!
So you are not so convinced of my Murano theory?
Michael