The Kew Gardens 2009 was listed at a starting bid of £50 – 100 times its original value, or to buy now for £151.52.
At the time of writing, two people had bid on the coin and the price was sitting at £59.03.
Bidding is set to end on Sunday.
The 50p is one of the rarest coins in circulation according to the Royal Mint.
They said on their website: “If you were to ask collectors which coin got them started, the chances are it was the 50p.
“Over the years, the coin has been issued in a huge range of commemorative editions celebrating every aspect of British culture, from athletes to authors.
“The sheer variety has sparked a collecting craze but of all the 50p coins, the Kew Gardens 50p is arguably the most sought-after.
“Nothing gets people excited quite like this original 2009 design.”
They said that the Kew Gardens 50p stands as one of their “most iconic” and “loved” 50p coins.
Only 210,000 of the coins were put into circulation and most of them went to private owners, so the Mint said the chances of coming across one in change “are slim”.
The coin features an illustration of the famous botanical garden, with the reverse showing the Chinese Pagoda at Kew with a leafy climber wrapping around the building.
According to the Royal Mint, the Kew Gardens 2009 50p coin is the second rarest in the UK – behind only the Atlantic Salmon 2023, of which 10,000 less coins were minted.
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You can view the listing of the coin here.
The seller said in the description: “It is a part of British decimal coinage and holds significance as a collectible item amongst numismatists and coin enthusiasts.
“The Kew Gardens 50p coin is known for its rarity and unique design, making it a sought-after piece for collectors looking to add a piece of British numismatic history to their collections.”
It can be collected in person or delivered for £2.94.
