The Royal Mint has created a new 50p coin to commemorate 160 years since the birth of Sherlock Holmes author Sir Arthur Conan Doyle.
The Government has previously described the new coin - which enters circulation on Tuesday - as "harder to counterfeit than ever before".
Savers who keep coins in a piggy bank could lose out as the new pound coin comes into circulation next month.
The new 12-sided £1 coin has gone into production - a year before it is to be released.
More than 4,000 coins are coming off the production line a minute, and they will enter circulation in March 2017 according to the Chancellor.
When the new coin is introduced, there will be a six-month crossover period when the current round pound coins and the new pound coins are both in circulation.
The current £1 coin is being replaced for the first time in more than 30 years because of its vulnerability to sophisticated counterfeiters.
Britons are hoarding around £317.5 million in loose change in their homes, a new study has found.
Men are the worst culprits and tend to leave more loose change lying around than women, typically keeping £18.18, compared with about £10.19 for women, according to Lloyds TSB's findings.
One person in 10 has between £50 and £100 in change - while three per cent of those surveyed said they had more than £100 at home.
People living in the North keep the highest typical amounts at home, with an average of £18.24, while those living in Wales tend to hoard the least, with only £7.78 on average kept in change at home.
More than 2,000 people took part in the research.