I think the item is Scandinavian.
There was a post about these stoppers
Apparently way back they bored a holed through a cheap coin - a cork and ring hoop were then required. The wire would go through the cork and up through the laid flat coin where it would hook around the ring hoop as a pull - this was used in most Scandinavian countries in 'Ye Olden Days'.
Eventually factories started making manufactured versions of these stoppers - like on Ivo's decanter/bottle. So it has to be Scandi?
It is a beautiful item and great to have the stopper - I have Lars Hellsten for Skrufs and Orrefors and they are clear glass - all the stuff I have seen by him is mainly clear glass/crystal.
I think could still be Skrufs - different designer, say 'Bengt Edenfalk' or ....
Ruda - mmmmm - the moulding seems too shallow and the design (Union Jacks!) to controlled - Actually I take that back if Ruda could be Gote Augustsson - especially the bottle shapes he loved
There are quite a few smaller concerns as well such as Alsterbro, I have seen some textured work by them
All this just IMHO