i see that in Wikipedia's page the coordinates are automatically showed in the upper right of the screen.
i couldn't understand how to do that on my site www.wikimilano.it
Topic on Extension talk:GeoData
I would recommend to refrain from this idea.
It has been a dirty hack about 2004, and it is causing problems over problems.
There is no gap left in the interface for such coordinates. Therefore the hack is hoping that it does not cover any other element nor text. But the hack has no eyes and does not know whether there is a gap or not. It is a nightmare. Skins are changing, and for every skin version and amount of text a small place needs to be found. This does not work with mobile nor App.