The new twelve-sided £1 coin isn't yet in circulation, but several are already up for sale - despite the fact that selling them is illegal.
Although the new coins won't become legal tender for another two months, Royal Mint test versions are popping up on eBay. Some optimistic sellers are slapping on price tags of up to £220.
The coins in question are some of around 200,000 'trial piece' coins, minted for vending machines, supermarket chains and banks ahead of the new coin's launch on 28 March. The idea is to let retailers test and recalibrate their coin handling equipment, such as ticket machines and self-service tills.
Is your £1 worth £30?
But dozens of these coins have somehow reached the outside world, and are appearing on eBay for sale. While some early sellers were asking hundreds of pounds, the price now seems to have settled down to around the £20 mark.
The coins are marked with the words 'trial piece', and the reverse carries the Royal Mint crest instead of the correct design. They won't be legal tender even after the new coin's launch.
However, they are likely to be popular with collectors, with the trial £2 created in 1994 now selling for around £150.
The Royal Mint is currently making 1.5 billion of the new 12-sided, two-coloured coins. They are designed to be harder to counterfeit than the current round coin, and incorporate a hologram-like image that that changes from a '£' symbol to the number '1' when the coin is seen from different angles.
The design, by 15-year-old David Pearce, shows the English rose, the Welsh leek, the Scottish thistle and the Northern Irish shamrock growing from a single stem within a royal coronet.
Do you have one of these valuable £2 coins?
The fact that so many of the new trial piece coins have leaked out is bad news for the companies that were given them - they'll have to pay the Royal Mint for any lost coins at the rate of 80p each.
And in any case, the sale is actually against the law. Technically, the coins are still the property of the Royal Mint, which could halt the sales and demand the coins' return. It has done so many times in the past.
And recently, at least one purchaser was also asked by the Royal Mint to return a 12-sided £1 - so it's very much a case of buyer beware.