Neither do I. I've just gone right through the book to check.
None of the Caithness decanters have a flange on the rim which sticks out sideways, there is a round shaped one, but it doesn't have a long neck, there's one with a long neck, but the base is a sideways oval shape.
So the shape's all wrong - but it also just doesn't look like Caithness or Caithness quality - the neck looks a bit thick and uneven, the base looks marvered aound the polished out pontil mark.....
Sadly, I can't think what it might be.