The coin, which dates back to 1971 and is silver in colour rather than bronze, was found in a donation box used for unwanted foreign currency at the Royal Berkshire Hospital.
The two pence coin was auctioned on eBay, and was bought by a collector for 802.03 pounds, 'BBC News' reported.
Silver coins are mistakenly created when a blank cupro-nickel coin is left inside a barrel during the production process.
The coin was among those produced between 1971 and 1981 which are emblazoned with the words 'new pence' instead of "Two Pence".
Last year, a silver two pence coin from 1988 was auctioned for 1,200 pounds in Dorset.