Mercury glass vase

I have just been left this vase by an old friend. It belonged to her grandparents (which takes it back to Victorian times). A little research has told me that this type of glassware was only made for about 4 years, ending in 1851, so it must be around 160 years old. On the base (seal) it says E Varnish and co. London Patent. It has always been in her family, so I know it isnt a recently made copy.