That is intended for skimming engine heads. The vertical axis stone protrudes a few thou above the surface, and the head is pushed over by hand. Not really what is generally understood as a surface grinder which is a far more universal tool.
A proper surface grinder such as a jones and shipman works like the bed of a mill but often with a mag vice and is much higher geared so one turn of the handle brings the bedfrom one end to another.