hello - it may well be all that you suggest of it - on the other hand it may not

Am I correct in thinking this is an item of pressed glass? This may account for the less than perfect seating of the stopper.
Pressed designs were made in a variety of countries, and we would need to find the exact pattern, and maker, to feel confident in saying it was British.
Take it that you can't seen any marks or Nos. on the glass.
Fred has posted images of some pressed decanters, I believe, so it's worth looking at the Board's Glass Gallery archive just on the off chance you might find this design - possibly not but always worth a peek.
If I had to guess (never a good policy if you want the truth) then I'd have thought not C19 and more like 1920 - 1950 period.
