I think they mostly ever made right hand vases, I do not think your find a left, so in this case a pair is 2 , I think people in those days were just happy to have 2 to display rather than one, I know someone in Scotland who bought a pair of uranium John Derbyshire hand vases not long ago, but to find one is quite rare, in 5 years of going to hundreds of fairs I have only seen one and that was glued back together,
Davidson made a tall slag glass boot on a plinth in a left and a right and that is seen quite often in a right boot , but only very rarely in the left, I only last week bought a rare pair of blue Victorian flat back glass dogs which are a true pair, so there are plent of pairs out there, some being true pairs while others are just 2 items the same which still makes a pair
regards roy