That's very interesting pipe troutface. I have about 20 of the Hesson threaded tenon pipes and they all have the triangle stem logo and the inverted triangle shank stamping. From what I can see from the picture, yours appears to be of the exact same construction. Is there any WDC markings anywhere on the pipe?
I do know that an American by the name of Feldman partnered with Hesson to open a branch of Hesson Pipes in the US. The venture apparently failed and the American patents and tooling were sold to WDC. There are court records showing that Feldman owed back rent on the space he rented for the venture and the property owner tried to sue WDC for the back rent after they purchased the assets from Feldman.
I wonder if this pipe isn't from the period before WDC bought the patents or maybe Canadian produced in the facility that WW Hesson shared with Brigham pipes. Either way it's a very unusual find. It's in very good shape, enjoy!!