Sure looks like Royal Brierley Studio to me
I have had a small baluster? (think that is the description ) vase of theirs which was not signed, the same colour as yours. I currently have 3 of the Pink in different shapes - all of which are signed. One of them is the exact shape and size of the blue one I had so I know it was right.
Not sure why some are signed and some not - mine didn't look like a second in any way.
Nor sure if that helped at all - I suppose the quick answer is yes - some of them are unsigned