I'm on holiday so no access to books so I'm replying from memory. I'm glad you have the piece id'd by someone as knowledgeable as Bill. As far as I know, I don't think it's possible to date an Orrefors production piece in terms of when it was produced, only by when it was designed. (Expo pieces and some other pieces can be dated by the code on their bases.) In the 60's (I can't remember the exact year) Orrefors started a policy of stopping producing designs by designers no longer with them, so your piece could have been produced any time up to then. The only way I can think of checking is to look at Orrefors merchandising catalogues for each year and see if your piece is included.
As an aside, Orrefors production was severely affected by WWII. The export market virtually disappeared, for one thing. That's why Vicke Lindstrand was let go as a designer by the company during the WWII.