Well, there are a few flaws that might suggest a seconds. A bubble in the upper part, and the whole vase is not quite straight, it leans a bit to one side. But I like the shape of the base, and if I learn a bit more from this thread, it's been well worth its price tag. Maybe an attempt from a European factory in the 60s of 70s to make their own version of this type of design. For instance, I stumble over Belgian glass quite often, and I'm still scrambling to find more late 20th century Belgian reference books. I knew some Belgian factories were inspired by Scandinavian designs, though I don't know to what extent.
Another thing, it feels relatively heavy, weighs 800 grams. Could that mean it could be crystal instead of glass? Or is it just heavy because the base is so massive? I'm not sure yet how to spot the difference.