The coins became collectors' items in June of last year when it emerged the Royal Mint had accidentally minted coins without a date on them. The undated coins came about due to a re-design of the coins, which involved the date being moved from the tails side to the heads side. But the old Queen's portrait design, which did not include the date, was used for the heads side, leading to the coins being minted without a date.
The London Mint Office, a private coin collector company not associated with the Royal Mint, immediately offered consumers £50 each for the coins. They revealed recently that they had purchased over 700 of them since since the announcement of the error, with the highest number coming from people in Birmingham, closely followed by Liverpool, Manchester and London.
The London Mint Office has now doubled the amount it is prepared to pay for one of the coins to £100.