The Royal Mint and HM Treasury are calling on people to hunt down any remaining coins and spend, bank or donate them to charity before the end of Sunday (15 October).
After that, the 12-sided pound coin becomes the only legal £1 coin for use in shops and restaurants, although the old round pound can still be taken to the bank or donated to charity.
Julie Mason, industry communications manager at The Royal Mint, explained: "Social media is core to the campaign. Messages are both organic and targeted dependent on consumer research and business feedback. The campaign is using The Royal Mint Twitter, Facebook and LinkedIn platforms targeted at consumers and businesses. These are re-posted via HM Treasury and stakeholder platforms. Instagram and Snapchat have also been used for elements of the campaign."
First introduced in 1983, the old coin has become vulnerable to sophisticated counterfeiters, with as many as one in thirty thought to be a fake.
The new gold and silver-coloured pound coin is designed to be more difficult to fake, and the overall key campaign message – ‘The new 12-sided £1 coin. Better by design’ – debuted last October.
However, secondary messages have also been used throughout the year-long project, with the current call to action based on the phrase ‘Spend, bank or donate your round £1 coin’ reinforced at regular periods, said Mason.
Over the course of the campaign, channels have included national and regional media, including consumer and trade publications, radio and television.
Meanwhile, e-shots targeted individuals and businesses who registered for updates about the new £1 coin, while ongoing consultation and communication has been carried out with key industry stakeholders in the cash-handling sector.
A dedicated website www.thenewpoundcoin.com has been offering general information, communication resources and FAQs about the new £1 coin and the end of the round £1 coin.
The campaign has partnered with a number of spokespeople representing The Royal Mint and HM Treasury, added Mason.
They include Adam Lawrence, the chief executive of The Royal Mint and Andrew Jones MP, the Exchequer Secretary to the Treasury.
The campaign has also partnered with Children in Need’s Pudsey Bear, to encourage people to donate their old coins to Pudsey’s Round Pound Countdown.
The new 12-sided pound came into circulation on 28 March, so there has been almost seven months with the dual tender.
Although more than £1.2 billion worth of old pounds have been returned, there are still estimated to be millions in circulation.
Some retailers, including supermarket giant Tesco, have said they will defy the deadline and continue to accept round pounds for an extra week, while Poundland has said it will accept the old coin until the end of October.