I've got a few pieces like this, as the style was widely adopted. Not all the Coquille pieces have the white line. I have a small piece with only a small teardrop of blue on the bottom. It, like all the other Coquille pieces I have, is signed. Another piece is signed Magnor, which I'd have thought was a possibility for this one except for the ground out pontil. I also have a couple of pieces of what I think are Murano like this, including one with a very dark blue centre in the middle of a more royal blue, as described in the other thread. The Murano pieces are heavier (thicker) than the Scandinavian. A couple of Canadian companies also made similar pieces. Your piece looks like very thick glass with the ends even thicker having being pulled out. If so, I'd guess Murano.
From what I've read, there were a few glass workers who moved between Murano and Scandinavia (and Canada, for that matter), but, more importantly, the designers and managers were aware of what was being made elsewhere.
David