***
Hi Tony
It is always good to have lots of reference books, even though they will contain the odd error (or sometimes lots of them...)! I think I have about 50, plus a lot of PCA Bulletins and the PCC Newsletters.
A quick glance through some reveals that Sybille Jargstorf (writing in 1991) identified Riedel as a maker of coloured glass for canes, and she also showed a Riedel paperweight - but identified it as just 'Northern Bohemian'. In 1999 Peter von Brakel also mentions Riedel, and shows a couple of Riedel paperweights but again just identifies them as 'Northern Bohemian'.
In 2002 Marek Kordasiewicz published a book on paperweights in which he showed and identified a signed Riedel paperweight. I don't know whether there are earlier specific references - but maybe someone on GMB does?
Alan