Britain’s new 12-sided £1 coin becomes legal tender in three weeks’ time, with the current round coin disappearing from shops this year.
More than 50 million of the old coins are in circulation, and the Royal Mint says around one in 30 is counterfeit.
The new coin is claimed to be the most secure in the world, its shape and composition making it difficult to reproduce.
It also has a hologram and a so-called High Security Feature hidden within the coin and detectable at high speeds in banks and cash centres.
Commercial Secretary to the Treasury, Baroness Neville Rolfe, said the technology would “help to tackle the scourge of counterfeits”.
But its introduction means that pockets and piggy-banks full of the old coins will need to be swapped or spent before they cease to be legal tender on October 15.
After that date, they can no longer be used in shops but can be taken to a bank.
The old coin replaced the Bank of England £1 note, which ceased to be issued at the end of 1984