A small batch of special Brexit 50p coins minted with October 31 are expected to become collectors' items now that it looks almost certain Britain will not have left the EU by then.
The coins feature the date of October 31 2019, as well as the words “Peace, prosperity and friendship with all nations”.
Chancellor Sajid Javid had asked for three million of the coins to be in circulation ready for the mooted Brexit date, with seven million more to follow within a year – but at least 1,000 have already been created as part of a trial.
But Britain is now unlikely to leave Europe by October 31, as parliamentary wrangling last night made a Brexit extension or general election more likely.
If Brexit is delayed, any coins with the October date would effectively have an error, increasing their interest to collectors.
A spokesman for Change Checker, coin experts, said: "Error coins do cause a lot of interest with collectors."
A 50p "error coin" is being sold for up to £600 on Ebay, a Battle of Hastings example with imperfect edges. Others, such as a Girl Guide 50p with a printing mistake, now cost £255.
Ebay sellers are already charging pre-order customers £7.48 for one Brexit 50p, an increase of almost 1,400pc.
The value of any October 31 Brexit 50ps would be reduced the more of them entered circulation. Andrew Hagger, of finance specialists Moneycomms, said: "It’s only if you get a limited amount that they have the quirk factor."
The Royal Mint regularly issues special coins to mark national moments, and these can be very valuable.
The rarest 50p coin in circulation is a coin depicting the Royal Botanical Gardens in Kew which has sold for £175,000 on eBay.
The production of commemorative 50p coins released by the Royal Mint has increased significantly, according to Telegraph Money analysis.
Eight new 50p coins were released between 2000 and 2009. Since 2010 there have been 22, not including 29 variants of the 2012 Summer Olympics coins.
The Treasury has been approached for comment.