I don't think it was an unfinished piece: I think it was a finished paperweight that was badly damaged at least once before. Look at the base view: the red/white staves are all polished off flat, not drawn in to the foot, as at manufacture. Someone has repaired a damaged base by polishing it flat and adding a new foot. At that time they probably reduced the dome to the shape it is now. And then it has been broken again...
I suspect it may turn up again with a new foot, or reduced to a modest sized paperweight.