Good point, Frank. Mine was a generalised statement made without a great deal of rigour in my own reviewing

I'll take this opportuntity to clarify:
Yes, the usage is certainly proven for some canes although I don't think that I, or anyone else, has yet fully documented which canes those are. But those who were at the Ysart Glass Conference may recall that I covered some of the examples in my slides.
The full version of my intended comment should have been, "I suspect that there are
many more canes, apart from those already known, which have been used in Paul's work and also in that of Salvador and Paul's brothers at the Ysart Brothers (Vasart) works."
(Oh, and for good measure, although there is (almost) no actual evidence to support the idea, I cannot rule out the making of some millefiori weights and ink bottles by Salvador in the 1930s - which, if they exist, could also contain canes that Paul used in his own early weights and bottles.)
The set of canes that Frank mentions as shown in the Ysart Glass book were eventually passed on to a paperweight collector who was a contributor to the book. They were later photographed, still on their sticky base (akin to Blu-tack) as end plates, not for John Simmonds' book, but for
Scottish Paperweights by Bob Hall, published 1999. They were also shown earlier, on page 63 of
Paperweights by Pat Reilly, originally published 1994 (now in a reprint version).
And those canes also nearly made it to my own web pages, but my photos turned out to be unusable and I have not since bothered to get fresh images!