It's amazing how much Carnival is spuriously "attributed" to Sowerby. It used to be that if someone didn't have a clue who made a piece (or couldn't copy someone else's research) then they would wave their arms and say "It's English". Sometimes now they wave their arms and say "It's foreign" or "It's European". And then sometimes they go the whole hog and say (without any proof at all) "It's Sowerby".
Look at all the "Thistle and Thorn" items and "Spilt Diamond" creamers attributed to Sowerby with not a shred of evidence.
I have considered the Towers vase on a number of occasions and I have also discussed it with Chris. Here is what I currently feel about the Towers vase (based on the evidence available at the moment).
The Towers vase is often attributed to Sowerby with (as far as I can see) no firm proof. In fact this item was produced by Davidson’s. But (and it’s a big “but”) the Towers vase was made by Davidson’s from 1961 and not before! Prior to that it seems the mould actually belonged to Matthew Turnbull. So…did Turnbull make Carnival? Probably, but more proof is needed. It is very unlikely that the Towers vase was made post 1961 in Carnival by Davidson - there would be proof and records. There are neither, as far as I am aware.
Glen