Anita and Rose - sincere thanks for your suggestions. You're right, of course,it is very attractive, although probably not my cup of tea, and if it is from your side of the water, then maybe someone else will recognize it. I stabbed rather quickly with the oriental attribution, but to be honest I don't know if they have been producing pieces with this sort of iridescence in recent times, and must admit I didn't look in the books before I posted
The similarity to LCT's 'Favrile' or Steuben's
'Blue Aurene' is apparent - although I don't really think it has that sort of age, unfortunately (with the iridescence it's difficult to assess age - although don't think it was made yesterday). My books, although showing a fair few examples of States and Continental pieces don't unfortunately show any base pics. What appears to be a slightly highlighted thin shiny trailing seems to come closest to some of the Durand pieces. However, I'm sure it is nothing so auspiscious as those factories. Thanks again.
P.S. Do I assume 'flume' being the process, Rose? and no, can't see LCT on its bottom