Princess Diana's 'Black Sheep' Sweater to be Auctioned for Up to $80,000

Princess Diana's iconic sheep sweater will be auctioned by Sotheby's in August
The sweater was discovered in storage after over 40 years
Diana wore the sweater to Prince Charles' polo match in June 1981
The sweater is estimated to sell for $50,000 to $80,000
Diana wore the same design twice, elevating the significance of the original knit