Thanks for the suggestion, Christine. I didn't know that was an indicator.
I have another couple of water sets that also have ground rims (all 3 sets are very carefully and subtly done), so that's a direction to look in for those.
I got an email this morning suggesting that this blue set might be by Jacob Bang for Kastrup, based on a decanter and vase in Andy McConnell's Miller's 20th Century Glass, p144, a possibility that I had missed.
Does anyone have any thoughts on that?
Thanks,
Chris