hope m doesn't object too much if I piggy-back on this thread.
Attached are pix of a green bowl (identified some while back by Nigel as SW/RB) - plus a vase of identical shape and dimensions to the original post here, and which matches the colourway/bubble construction of the bowl. Would therefore seem to be a very good chance both green pieces are SW/RB.
There appear to be consistent differences in bubbles and halos, between this factory and Nazeing, although I think there is a need to look at a few examples in order to 'get the eye in'. Of course it does help if it can be shown - as pointed out with the 'Rainbow' vase - that this was not a shape produced by Nazeing - but not quite so simple eliminating bowls, where many factories offered similar shapes - and this is where knowing your bubbles/halos and recognizing colourways is essential. Having looked at Geoff. Timberlake's book, I don't think this 'green' was a colourway offered by Nazeing, but that is my opinion only.
The bubbles and halos in these pix might be compared with the Nazeing material shown in current post in 'Glass' - although it seems there is perhaps some doubt that all shown there is Nazeing .... http://www.glassmessages.com/index.php/topic,50932.msg288557.html#msg288557
It's unfortunate that Charles Hajdamach's C20 book is quiet on some of this material, but guess we can't have everything in one book.
The logic of why the term 'Rainbow' escapes me - possibly the original range of colours offered was varied.
From the very few pieces of both factories that I've seen, I'm inclined to suggest that the ground/polished pontil depressions on SW/RB material might just be of a higher quality, larger and shinier than pieces from Nazeing - although as I say, I have only a very few items, so that is just a personal and speculative opinion.
I've tweaked the pix a little with Picasa, mostly to accentuate the halos and bubble areas, so the green has been distorted slightly - apologies.