thanks to Christine and Rosie - and appreciate the link. The mark on my piece was very difficult to see, and I very nearly overlooked it, but as we know, the backstamp is easier to see on some pieces than others. In view of the lack of information on SAWREX, I'm surprised in fact that there is even one piece on ebay. Looks a nice tumbler, and presumably quite collectable - so must keep an eye out for more pieces.