thanks Rob - certainly does look very much like a gadget mark - so my original thoughts on dating may well hold up. Another possible use might have been for gin, and they may equally have been of Continental manufacture.
In view of their age, type of glass and shape, pieces like this might have been made almost anywhere in Europe.
Having said that, C19 drinking glasses have a lot of history in them - who might have used them and when, and where - I always feel they have a lot of soul in them and are a great area to collect.
