Ok, thank you all for your responses and help
Sue I like your thinking re the chemists bottles. I was also thinking that the little opaline rectangular boxes with hinged lids were also very much in vogue and a square shaped bottle would sit better with those as a set rather than a round bottle.
So... my initial thoughts were could it be Harrachov Chrysoprase or Baccarat Chrysoprase hence my question about Bohemian or French.
But then looking through the net, I thought if it were Baccarat would it not be marked in some way at all, if they marked the stopper then surely they would have marked it Baccarat somewhere? Much Baccarat does appear to be marked, but I wonder is it all marked?
Then, having done a bit of searching I did find perfume bottles in this exact same shape body with the cut sides and that appear to be the same or very similar size to my bottle (difficult to be exact because I don't know whether they are measured with their (different to mine) stoppers or not). My bottle is 11.5cm to top of neck and just over 15cm to top of stopper. The ones I've seen say they measure 13cm which they would be, with a flat stopper in, I guess if the bottles were 11.5cm. The stopper is a perfect colour match and perfect fit so I'm sure it is a match and there is a minute number 10 engraved on the inside rim of the collar of the bottle (thanks Paul, for making me double check). However they appear to all have some ormolu decoration on them (the stoppers are ormolu decorated as well). They are all marked attibuted as French (but not Baccarat) and I wondered could the glass could actually be Bohemian, but then I surmised that for the moment no, I have no reason so far to believe they wouldn't be French made opaline with ormolu.
The ones that are attributed as Bohemian green opaline appear to have lots of gold decor on them, as opposed to ormolu on plain opaline. So for the moment, I'm thinking not Bohemian perhaps.
The pontil mark is beautiful, round, polished beautifully and perfect. Would glass made in Italy or Sweden have that kind of pontil mark? (forgive me my ignorance - this is just my thoughts).
Which brought me back round to France (shape and immaculate pontil mark) or possibly England.. and of course now Ivo has added in Belgium.
My question about the dates of it was because the pieces I have seen in the same shape and similar size are all ormolu decorated and dated mid 1800's - late 1800's. I just wondered whether it might be later because it is plain and undecorated.
So would the numbering of the stopper and neck indicate a particular country? I have to say they don't look like European script, they look like English script to be honest *the number 1's I mean. so could it be an English piece? if so would Richardson's be a possible?
So that's where I 'm at so far

and possibly that is far as I will get

I'll let you know if I discover anything more (highly unlikely I know).
Many thanks for replying and helping.
m P.S. it is in perfect condition :hiclp: