Pix don't show the depth of blue - this really is a true bristol blue colour. I've looked on the Bristol Blue Glass site (Bristol, U.K.) - as I'm assuming quite possibly theirs - although don't see this pattern shown, but understand they do use a dremeled backstamp like this. Pontil mark is slightly sunken and snapped - height of jug is c. 4.75" - 120mm - handle is copying period style, and there are a few period white stones for good measure. Unfortunately, someone had been using this for their Ready Mix concrete, and even after a few Sterodent tablets there's some deposit around the inside of the rim.
I've not previously seen or bought a piece of Bristol Blue Glass, so hope someone able to confirm if my thoughts are correct or otherwise, and thanks for looking