Adding a taper to the bowl isn't "his spin." It's the normal Danish Billiard shape, impressed so deeply on the Danish psyche by Ivarsson and his children, almost every 'traditional' pipe shape gets the Ivarsson design treatment.
I also forgot to mention, what is this “Normal” Danish Billiard shape you are referring to? Are you simply talking about a typical Billiard shape?
If you ask, where is the birthplace of the briar pipe, that is considered Saint- Claude France, and then where many traditional shapes were also suppose to originate from, including the Billiard.
The History of Saint-Claude, France | The Birthplace of the Briar Pipe
Learn more about the early years of briar pipe making with this look into the history of Saint-Claude, France.
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