I would agree with Richard that the type of faceting on this example is unusual. I cannot recall for sure whether I have seen another one like it. Maybe, maybe not, although I do have some vague memories of seeing others.
For anyone looking in books and elsewhere, please note that the commonly used name, "Seaweed", is not what Strathearn called them. The name was "Tropic" (as shown in Richard's album site). But "seaweed" does seem more descriptive, doesn't it!
Regarding the comparisoon to the pic in the James Mackay book, it does indeed look to be the same weight. But I spot certain differences. Perhaps the book image was cropped at the base, and this would explain the apparent difference in width near the base and possibly also the (minor) difference in apparent facet shape, too?
But looking at the internal elements, it does look as identical as you could get. Bearing in mind that all Tropic weights (with and without facets) were hand-made (i.e. no standard crimp was used, to my knowledge), the "weed" bits would most likely differ in several aspects for each weight.
My copy of the Mackay book is a reprint (1981), rather than a revised edition, so I imagine that the content is as per the original (copyright 1973). That would confirm that this type of unsual faceting was done between 1964 and 1973, so perhaps there were others, too.
Keep your eyes open, folks.