Sue, thank you very much. Based on all my searching, I'd say they are pretty uncommon, too!
Loetz made rainbow glass, as did Harrach, and apparently also Stevens & Williams, and some American firms. But they are all quite hard to find. I just have never seen one with a cut rim quite like this, so need to start broadening my search. You know, the colors are very much like tartans, now you mention it!
Michelle