The shape, with its sloped shoulders, looks similar to the kuttrolfs being produced by Glimma in the 1950s/60s.
I had some reference images for Glimma decanters, but I seem to have misplaced them, or might have lost them when my hard drive died last year. Edit:
Ignore that last bit - found the photos. I'd say Glimma is a fair bet for the manufacturer, based on the shape.