Interesting theory, Bernard, but would rivals have done this? I don't know. It's possible (I never rule anything out). However, there is a link to Turnbull that I have been chewing over for a little while now. I'll explain.
If you go to Chris Stewart's Cloud/Davidson website and select Davidson glass, Post World War 2, you'll find a posy vase called M.T.1 posy set. It's shown in flint, green and red with a date of 1961. ..... but this posy vase is known in Carnival Glass and it's called "Towers". It is usually "attributed" to Sowerby, but unless Adam D knows differently, it would appear that it was Davidson. Well, at least from 1961. But that isn't the right time for Carnival. The 1920s and 1930s were most likely.
It seems (according to the Stewarts) that the mould for this posy could have previously belonged to Matthew Turnbull (M.T.) So the new question is, did Turnbull make the posy vase in Carnival?
If so, then possibly other unattributed pieces could well be Turnbull. The Thistle and Thorn pieces would be possibilities, as would this "Derbyshire" vase.
We may be onto something. A clincher would be if anyone has the "Thistle and Thorn" creamer and sugars in opaque white with a trademark.
Until more evidence comes along I am only guessing (but I hope it's intelligent guessing :lol: )
What do you think, Bernard?
Glen