Michel Grand has pointed out to me that diagrams are also in the book 'Noshi' by Isao Honda, published, I think in 1964, where he calls it a Tortoise-Shell (because it is kind of hexagonal in shape).
Honda says nothing about its origin. I thought at first this settled the matter and that it was therefore not by Yoshizawa. Then I remembered the dreaded Honda / Yoshizawa controversy which, as far as I know, has never been successfully resolved. Nothing is ever simple ... Dave
