How do I open the back of a gustavsberg toilet?
Guestavsberg has product manuals available on their website:


http://www.gustavsberg.com/28081.asp


Find the page for the specific toilet, then from the product's page, go to 'downloads' and look for the link labeled 'assembly', which also includes information about servicing it.

It looks like some of them have two bolts connecting in from underneath and then you can slip the whole cover off; others have round thing on the top that you press down then give a quarter turn and pull up.