The UK and Ireland have ratings on the front, spine and back - though a little more discrete than our Aussie friends. I hardly notice them anymore - hard not to notice the Aussie’s classification 😃
I imagine a few film buffs down under may opt for a custom cover?
http://www.bbfc.co.uk/what-classification
http://www.ifco.ie/website/ifco/ifcoweb.nsf/web/classcatintro