oh yes, also that (In my opinion it does look like it could have originated in the 30's - but I'm beginning to get slightly embarrassed that I'm questioning all these titles never mind other people's id's, believe it or not
With regards your comment re that white over pink crackle vase - aha ... I wondered where the 'Webb' attribution had come from as I'd seen my little yellow vase identified as Webb.
I have another point though -
I'm just going back to The Crystal Years description of the 'Arboresque' range:'This was a treatment carried out in the early 1930's and used a glasshouse effect of trailed uneven coloured glass, mainly of jade green and rose, on to the surface of clear crystal articles.'
Unless the author did put the wrong description next to 'Arboresque' (and would he really - is he the most likely person of all the authors and books quoted above, to get it wrong? Not saying he didn't but on balance he wouldn't have been my first port of call), I really do think these vases and bowl match his descriptor. http://www.20thcenturyglass.com/glass_encyclopedia/british_glass/stevenswilliams_glass/stevenswilliamsglass_home.html
Is it possible that, given Stevens and Williams were known for their immaculate threading and trailing, by comparison to those type of pieces, this trailing on these vases we know as rainbow would have been considered 'uneven' because it was not immaculately spaced and trailed, but rather freeform. I don't know what the author meant by 'a glasshouse effect' but I do wonder if he meant what we would consider today to be 'studio' type glass.