A nice lamination / planchet flaw with parallel streaking.
(http://www.australian-coins.net/gallery/albums/userpics/11067/50_1972_streak_1.jpg)
(http://www.australian-coins.net/gallery/albums/userpics/11067/50_1972_streak_2.jpg)
love the "streaks".
Don't look Ethel (https://www.youtube.com/watch?v=XtzoUu7w-YM)