But this is one we'd be more happy than most to sell on - because it could be worth up to £1,000!
The coin was made of a cupronickel - a copper and nickel blend that was used to make 5p and 10ps - instead of bronze, making it worth 50,000 times its face value.
It was discovered in 1988 by the owner of a petrol station but it is only going up for auction in Sherborne, Dorset this week.
Richard Brommell, from Charterhouse Auctions, told the Mail on Sunday: "The Royal Mint can produce the odd anomaly but this takes the biscuit. It's a very difficult thing to value because there are no comparables.
"We say £100 to £200 as an estimate, but if two people are bidding for it, the coin could for more than £1,000."
Crikey! Sounds like a good deal to us!
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