Thank you both Christine and Ivo. Ivo I'm off to investigate spelter in more detail and I love your comment
'when quality and taste went down in favour of volume'

It
is beautiful (looking at it now 140 years later), but I know what you mean. It is missing it's three links round the neck of the metalwork and a chain it should hang on as well I think.
I agree on the colour - it's gorgeous and whilst my photo doesn't show the base well, the base of the glass (mould?) is finished beautifully with decreasing concentric circles ending in a tiny circle in the middle. No bumpy finish.
I've added some more pictures of the stopper (unwashed) and close up of the glass which hopefully will come out well.
Thanks again for all your help

m