champ mastery sign above head command?

back in the video on this page http://na.leagueoflegends.com/en/page/features/champion-mastery it shows people in game showing mastery levels above thier champ's head

now i cant for the life of me figure out how to do this. i know you need to be champ mastery level 4 or 5 and i read the hotkey was Ctrl-5 in a riot post; but i tried that and it does't seem to work for me.

is it possible to do this still? if so, what command do i enter?