A new 12-sided £1 coin starts to enter circulation next week, as the old "round pound" will not be around for much longer.
The new coin, which enters circulation from Tuesday, has been described as the most secure coin in the world. It boasts high-tech features, including a hologram.
It can be used alongside the old pound coin until the round pound ceases to be legal tender on October 15.
The new coins have been made at the Royal Mint in Llantrisant, South Wales, at a rate of three million per day.
They have a gold-coloured outer ring and a silver-coloured inner ring and are based on the design of the old 12-sided threepenny bit, which went out of circulation in 1971.
It might take a few days or weeks for people to start seeing the new £1 coins turn up in their change as they gradually filter into general use.
People using some coin-operated machines may also find that keeping a few spare round pounds in their wallet will prove handy for a while. Not all machines will work with the new coin from the date of introduction.
The Automatic Vending Association (AVA) estimates that on March 28, when the new coin goes into circulation, around 85% of vending machines will be able to accept the new £1 coin and all will still accept the old coin.
It said that with around half a million vending machines across the UK, ensuring all of them are upgraded is a "major operation".
The body has estimated that all vending machines will be fully upgraded by the end of the transition period on October 15.
Jonathan Hart, chief executive of the AVA, said the upgrades needed for the new £1 coin will cost the vending industry an estimated £32 million.
He said: "We support the Royal Mint and the Treasury's actions to protect the integrity of currency in the UK and reduce the level of fake coins in operation."
£1 coins were first launched on April 21 1983 to replace £1 notes. The Royal Mint has produced more than two billion round pound coins since that time.
The production of the new coins follows concerns about round pounds being vulnerable to sophisticated counterfeiters. Around one in every 30 £1 coins in people's change in recent years has been fake.
The Government has previously described the new coin as "harder to counterfeit than ever before".
People have been urged to return their old round pounds before they eventually lose their legal tender status. They can bank them or spend them.
Around £1.3 billion worth of coins are stored in savings jars across the country, and the current £1 coin is thought to account for nearly a third of these.