Errare humanum est
I've just finished a few features on errors in philately, so I'm probably still very much focused on that, but it's not why I bought this set. I only got it because I thought they looked nice! It is the 1952 set issued by the German Democratic Republic or DDR, marking cultural anniversaries. And it is the top value which displays the error.
The three other values mark the 150th birth anniversary of the writer Victor Hugo on the 12pf value,