Sorry, I can't help, Anne, but I'd love to know too. :thup:
I have a small set of these sherry glasses in Smoke, and Caithness is not a maker I'd considered at all - just not Caithnessy, I didn't think, with the weird rim bit around the foot where it connects with the stem, and I thought they were a bit lightweight too.
Also, I see a lot of Caithness around and I don't see these often.
However, you've solved the mystery
and they're definitely Caithness! :clap: :clap: :clap: