Gosh, this one goes back a while! I've still got them boxed up in the attic.
I'm not entirely sure that they are Caithness, as all the verifiable lamp bases I've seen from them have been cased in clear. These pieces in question are not.
Also, not sure what I was on about when I said "They have very typical Caithness bases" - because they really haven't. Ah, the smell of inexperience!