British Coins, G Elizabeth II, half sovereign, 2004, head r., rev. St. George and the dragon (S.SB4), certified and graded by NGC as Mint Error, Obverse Struck Thru, Proof 69 Ultra Cameo
NGC explains 'struck through' as follows: 'Struck throughs occur when a piece of foreign material comes between the die and a planchet during striking'. The flaw on this coin can be seen to the right of the queen's forehead.
(150-200 GBP)