Czesław Słania's 70th birthday, Sweden

Some older stamps on the front and back of this cover from Sweden and possibly posted from one of Postnord's processing facilities. I believe this is a philatelic postmark. It is clearly handstamped and not machine cancelled. The large stamp on the right is from a 1991 sheet that commemorates the 70th birth anniversary of famous stamp engraver Czesław Słania.