Uhhh, I totally stand corrected Petieken, you are right !!!
The thing is that your ground pin is in the wall socket, but some (older) plugs ONLY have that hole to accept that pin, instead of the "edge" connectors like we (and the German) use. The plug you picture there is "all round" for both systems and what you usually see these days.
The Berzerks had this plug, but f.i. the Centi's had the older type.