Long shot- Hydraulic table

I've have had this hydraulic table (is that even the best name for it?) for some years now and I'm now selling it. But I have no idea of the lift capacity. Is there a way to find this out/ safely test it? It happily lifts the 100kg robot, and can also lift my dad and I (total around 140kg).

I've attached some photos in case it helps people. Many thanks.

James.

http://imgur.com/2La7RH2,xPDlXpz

Most of the "light commercial" ones go up to 300kg.

And sorry, we have one with bigger wheels.

Looks like the 150kg version, thats what most of the roboteers use. the 300kg ones tend to have bigger platforms.