and is found mostly on translucent white and blue glass - possibly never on green - nope, sorry, still rubbish.

Would seem that Opaline was produced in most colours at one time or another, apparently, mostly in pastel shades. Very de rigeur after about 1823 when popularised by Baccarat, and the French were good at it. Problem with getting an accurate attribution for Opaline (i.e. the fiery orange inner glow), is that you can't - unless the piece is yours and it can be back lit properly - see the attached pictures. In books, opaline fequently looks just like Alabaster or Vitrified, and often (apparently) the workers called any piece of whitish semi-opaque glass 'opal' (quoted from Cyril Manley). There is a lot of reference in books re 'Opal' glass and Vitrified Enamelled' glass, but whether it all contains metallic oxides (to creat the 'sunset glow') may be doubtful.
None of which has much to do with this green 'urn' however

, it certainly isn't genuine opaline - and unless someone has a better idea, I have chosen Barrie Skelcher's colour description of 'translucent jade green'. This piece is much more transluscent than the pictures show.
Did Christine have Cyril Manley's book in mind when suggesting Richardson?? He shows a couple of pieces of C19 'Vitrified Enamel Coloured' glass (green) plus similar with white strap handles (but no attribution for that) - mine could be C19, although it doesn't have any gilding around the edges like so much of the genuine C19 'Chrysoprase' pieces, so this point may indicate it is C20, but I really don't know.
Manually blow moulded seems more likely - do you mean manually blowing down the pontil rod?
I will now follow up Ivo's reference to Nason - where do I start

References: 'Decorative Victorian Glass' - Cyril Manley.
'An Illustratged Dictionary of Glass' - Harold Newman
'The Illustrated Guide to Glass' - Felice Mehlman (very good inexpensive book).