I associate this shape of carafe, with the sloping neck rather than pronounced shoulders as being of early production, as evidenced by the polished pontil marks found on them.
I have a blue (flat polished base) and an amethyst (polished pontil mark) one of this height, and a couple of stunning blue, cloudy and iridescent ones of 11.5", both with the polished pontil mark which indicates Harris/Boffo period.
Normally, though they appear with many more colours from silver salts and often with good iridescent streaks!
Later carafes are ~ 20 cm tall, and have pronounced shoulders, much more of a bell shape.