By coincidence, I just found a good prospect (I hope): this particular vase might be German, Gral glas, by Konrad Habermeier.
I noticed this one when I was browsing this site:
Mod: link removed as it's carrying a trojan drive by download, website owner has been notified and link will be restored once the site has been cleaned & checked
(scroll to the bottom). This collector is not always accurate with his attributions, but he does have a lot of German glass.
Anyway, the similarity I noticed was how the blue changed colour from dark at the top towards lighter at the bottom, and the way the clear encasing wasn't covering the entire piece.
So I searched for a bit online, and I found another that had a few similarities (blue from dark to light, patterns in clear encasing):
http://www.liveauctioneers.com/item/5373714I have seen some other examples from Habermeier in the 50s where he made patterns in encasing clear glass over a coloured interior.
Unfortunately, I couldn't find this specific vase or anything so similar that it would remove all doubt, but I hope that it is one step closer.
For those interested in Gral Glas, I also found a link to the Hentrich glas museum in Düsseldorf, where a Gral glas exhibit is scheduled for feb to may 2011 (as the Gral glas book is expected to be published in februari 2011 as well, that might be a deliberate combination).
Let me know what you think...
Astrid