as always with multiple input there's a problem with getting sidetracked - as with any attempt at dating, it's usually the case that there's a need for maximum features with positive definable dating characteristics, before leaping into a particular era. IMHO, polished pontil depressions are a tad too vague, and Bristol blue has been around since the Romans, apparently. But it's the 'string ring' that seems out of place here - assuming that's what's on the neck - they've not been on bottles for several centuries - so assuming this item is a serving bottle than presumably the ring is purely decorative and not made for use.
This one may well have been made as a table serving bottle for spirits, but looking at examples of blue spirit bottles they appear, usually, as bulbous shapes or as spirit squares.
The Bohemians and Germans drank their Rhenish stuff from green or red glasses and made coloured bottles, and perhaps in the U.K., as suggested, we used clear bottles as Brits. preferred red wine (picture of a clear bottle attached - probably first half C20 - it's a perpendicular cylinder decanter and not a serving bottle - as it has the No. 46 on the pouring rim, but came without a stopper).
But who knows - this is an attractive bottle but with an elusive birth date, unless we can find some corroboration in the form of a known datable example for comparison. Dating this one is all the more problematic as there seem to be very few examples of serving bottles compared to decanters with stoppers, of which there are very many, and blue ones even more rare - if pushed I'd go for either a repro item from the 1920/30s, or back nearer the middle of the C19 - wear on serving bottles can seem disproportionate if they're used most days for half a century, or if you're a lush
