Thought I'd post this out of curiosity. My mother recalls buying them in the late 1950s and they were sold with fish paste in them, but with the intention that the jars could be used for other purposes – a deliberate promotion by the makers.
The quality of pressing is very high: a 3-past mould appears to have been used, but it is not possible to detect a seam across the ball optics. The close-up also shows the remarkable optic effect.
The base is a bird-bath and a ground base rim. It measures 9cm tall and 5cm across the rim.
But who could possibly be the makers?